since there are a number of other reviews describing this dap, its layout, ui, etc, i will confine myself to some observations about sq and relative value.
 
my main points of comparison are the ibasso dx90- the first dap i got, and the questyle qp1r- the last dap i got.  the n6 was in between in every sense:
 
1. bass - it was only after i listened to the n6 that i realized that the dx90 bass was somewhat loose and bloated.  the n6 has a tightly controlled bass with rich tone and deep extension.
 
2. mids- solid mids, in no way recessed, with rich tone.
 
3. treble- i am a little dissatisfied with the n6's treble.  it has good extension but is thin and lacks much texture.  this was made clear to me when i got the qp1r, which has a richer treble.
 
4. soundstage- i agree with those who describe the n6's soundstage as very wide but not very deep.
 
5. imaging- the n6 provides terrific placement of each source.  there is a sense of air around each instrument, as if there is a space surrounding each instrument as a kind of frame.  this is in contrast with both the dx90 and the qp1r.  the dx90 sounds a bit congested when a/b'd with the n6.  the qp1r doesn't have that air framing each source.  it is not congested, but it is as if the sound exactly fills the space.
 
6. value- the dx90 is solid value at $400.  at times the n6 is available for $500 - see the price graph at camelcamelcamel dot com.  if you want the n6 at that price you can set a price alarm there.  that's how i bought mine, and i think that for $500 the n6 is an even greater value than the dx90.  this assumes you don't mind the bigger form factor, the heavier weight, and the ability to swap batteries.  the qp1r has the best sq, but costs $900.  there are people in the qp1 thread saying that they perceive the qp1r as having better sq than than the ak240.  but if you're shopping in the high end realms of the 901s, the ak240, and the lotoo paw gold, then you're probably not even reading this review, but if you are you should consider the qp1r.  if, otoh, you are comparing daps in the dx90 price range relative to the n6 at $500, remember that the n6 gives you terrific sound with enormous bang for the buck.   if you are comparing the dx90 @400 to the n6 at the $600 it usually sells for, then it's more a value judgement.  the n6 definitely has the better sq but is 50% more expensive.  

THOSE GREEN BARS DO NOT REPRESENT THE RATINGS I GAVE.  THEY APPARENTLY CANNOT BE CHANGED WHEN I EDIT MY REVIEW.
 
i participated in one of the fiio x5ii tours.  i would like to thank fiio and all those who helped organize the tour.  i was eager to participate because i almost bought an x5 [1st gen] but then decided on a dx90 - i'd never heard either when i made that decision and wondered how they compared.  so given a chance to listen to the x5ii, i signed up.  my goal was to compare sq on the two daps. 
 
i am grateful for the opportunity provided by fiio, and feel badly to post a critical review.  yet if a friend were to ask me for a recommendation, it would not be the x5ii, and i wanted to share my honest observations with the head-fi community.  
 
other reviews describe the physical object, the interface and controls, and i'm not going to repeat all that.  i will just discuss sq.
 
the music i used to evaluate it were the following tracks, all redbook, flac encoded:
 
charlie hayden and pat methany - first song for ruth  - i use this the evaluate bass. hayden goes very deep in his solo.  a four string bass gets down to about 30hz, a five string about 25hz.
 
melos quartet - schubert's quartet 14 "death and the maiden" - 2nd movement - andante -   i use this track to evaluate treble - the violin can get up to about 3500hz and of course produces overtones as well.  the first violin in this movement has runs getting quite high.  i also listen to the cello to see if the richness of the instrument is fully conveyed, and i listen to hear how well the individual instruments are defined.
 
radu lupu- schubert piano sonata 18 - 1st movement - i have 8 versions of this sonata and lupu's is for me head and shoulders above the others.  in the first movement the left and right hands sound pretty far apart, i.e. the left hand's bass is quite separate and distinct from the right hand's treble.
 
kleiber vienna phil - beethoven's 7th symph- movements 1 and 2 - i use this to hear how the massed instrumental sections sound.
 
these are tracks i have heard many times and know very well.
 
my method was to first listen to a track on the x5ii and then on the dx90, and then check my impressions by listening again on the x5ii.  i listened directly from HO via my k812's - the best headphones i have that can without doubt be driven by these daps without any extra amping.
 
i had certain expectations as i approached this evaluation.  from things i'd read, i expected the x5ii to sound somewhat colored and, in particular, warm.  the first thing i noticed when i listened to the hayden/methany cut was that my expectation was wrong.  the x5ii sounded quite pleasant and quite neutral.  "hey," i thought, "this is pretty good."  i was shocked, however, when i played that cut through the dx90 - there was a ton of bass i was experiencing that had been missing from the x5ii.  without the comparison i don't think i would have noticed, but the difference was enormous.  the bass gets low enough that i felt vibration in my lower throat and upper chest.  as a check, as i am writing this i am playing this track through my speaker system- and there's very deep bass, bass that the x5ii did not convey.
 
next i played the schubert quartet movement.  this sounded nice but the violin sounded a little thin.  i wondered if the dx90 would sound much different.  when i played it through the dx90, though, my immediate reaction was "AIR!" - something i hadn't thought about and wasn't looking for but it hit me in the face.  the sound was much more open and the 4 instruments more well defined.  i noticed that the cello sounded much richer - there's that difference in the bass frequencies showing up.  the violin sounded more textured, thicker.  i suppose this means that there are more harmonics reproduced, but i really don't know what is happening at the technical level.  the difference is comparable to a painting done with acrylics compared to the same image done in oils.
 
i decided to listen to some piano music and queued up lupu.  the left hand sounded muffled and distant, almost missing.  again the dx90 gave full accounting to the bass frequencies and the left hand was contributing fully.
 
i then decided to listen to some orchestral music.  here the difference was the increased texture and richness of e.g the massed violins in the 2nd movement.
 
i said i had certain expectations - the 2nd expectation i had was that the differences between these daps would be subtle and take work to discern.  this had been my experience when i compared the dac sections of the dx90 and the ifi idsd.  i had used coax out of the dx90 to run the signal through the ifi's dac and amp, and compared this to using the dx90's dac and running a line out to the ifi's line in so that the signal would go through the same amp.  i went back and forth many, many times before i finally concluded that the dx90's dual sabres revealed a bit more detail than the ifi's dual burr-browns.  i expected this comparison to be like that.  it wasn't.  the differences were very marked.
 
obviously this was not a blind comparison, and i suppose i could be somehow conditioned to the dx90's sound.  otoh i actually do most of my listening through my speaker system - vortexbox -> squeezebox touch -> DSPeaker anti-mode [just set to correct the room's effect on the bass below 150hz] -> nad c375 bee -> focal chorus 836v.  it is really my speaker system sound which is my reference for both daps, and through which i have great familiarity with my chosen test tracks. also, the differences were shockingly MUCH greater than i expected.
 
so i feel a bit of an ingrate saying all this, but this is what i heard.

i refer you to ljokerl's theheadphonelist to get the background on this iem.  the list is at:    http://theheadphonelist.com/headphone-list/#   and this iem is described at:  http://theheadphonelist.com/headphone_review/flc-technology-flc8/   
 
if you sort ljokerl's list by sound quality instead of average rating, you'll see that the flc8 is the highest rated iem [9.4] which is neither custom nor over $1300. in fact, the flc8 is currently selling for $343.    its average rating is lower because of its mediocre isolation, 3.5 out of 5.  for me this was an advantage- i have ety4's with custom tips if i want isolation.  otoh, i can wear the flc8's out and about, and have a better chance of not getting run over.  also, if i'm in a quiet place, i think the flc8 has richer tone than the ety's.
 
the tone is rich across the full spectrum.  i listened to some test tracks with the neutral settings it arrived with, and then exchanged one of the tuning plugs to boost the highs - i listen to classical and jazz, and the first violin in melos' performance of 'death and the maiden' sounded thin with the default settings.  but for my music, acoustic music, the neutral settings for low bass and upper bass were fine. the cello in the string quartet sounded good, and the iem's gave a good rendition of charlie hayden's double bass in 'first song-for ruth' [from his album with pat methany], which i use to test bass performance. the bass was full, tight and without bloat.  to listen full spectrum, i then played a piano sonata [schubert's 20th, uchida] and it sounded very, very good.
 
the set is ultra-comfortable, and a bargain for the sound quality you get, provided you can live with its mediocre isolation.
 
 
btw- i just did a little experiment, and you can use comply 400 series tips to get more isolation if you want. the flc's are NOT listed as "officially approved" by comply, but it works.  thus you can choose your degree of isolation, within limits.
 
but these are not deep insertion iem's, so they will never be as isolating as ety's.  they have rather short nozzles, almost like earbuds; they insert just a bit into the ear canals. although offering less isolation, the supplied single flange silicone tips are more comfortable than the comply's.  i haven't tried the MEElec M6 single flanges recommended for the flc8 by ljokerl, but they look virtually identical to the supplied tips.  
 
 
 
along with the flc8's bargain sound quality, as a bonus you get their flexibility in adjusting to the signature you prefer.

i won't repeat the details available in the review that's already been posted.
 
i got the ifi micro idsd for several reasons: one was that i wasn't sure my dx90 had a strong enough amp to drive the planar alpha primes that i recently bought.  the ifi micro has a very strong amp, capable of 4w output.  another reason i got it was that i was curious about how a different dac would sound- i have a dx90 with its dual sabre dac, and a gungnir on my home system with its akm chips.  the ifi micro idsd comes with a burr brown dac.
 
bottom line:  my dx90 could in fact drive the alpha primes pretty well, but they sound even better when i use the dx90 line-out to the micro's line-in, i.e. use the dx90's dac and the ifi micro's amp.  the greater power of the ifi's amp, plus its very impressive "3d" crossfeed feature produces a bigger and cleaner soundstage.  the ifi's dac was a disappointment, at least compared to the dx90's dac.  the dx90's dual sabres produce cleaner, clearer sound.  in comparison, the ifi's burr browns sound muddy.  i don't want to overstate this- if i had just listened to the ifi micro and not had the dx90 to compare with the very same source files run out through the very same amp [the ifi's via line-out-in], the burr browns would have sounded fine, perfectly acceptable  
 
the ifi micro is not a portable "on-the-go" device, it's too big and heavy for that.  i would call it "transportable," rather than "portable."  the heaviness of the micro is in part a function of its very large 4800mah battery - a trade-off desirable in some circumstances, not others.  
 
in sum, the ifi micro is a very capable, multi-featured, transportable device.  it will accept inputs via coax or toslink to run through its dac stage, or line-in to skip its dac and just use its powerful amp.  there are a multitude of adjustments that can be made depending on the power demands of your phones, as well as a choice of filters controlling how it samples.  [i only use pcm flac files and so used the bit-perfect filter.]

i've had my dx90 for some time, having bought it when the price was still about $420.  i thought it was a great value then. it's an even greater value now.
 
i'm using the 2.0.5 firmware because i'm happy with the sound and am not willing to roll the dice on any changes.   i find the interface exceedingly easy to navigate, but must note that i use a folder structure instead of tags, and so can't comment on tags and playlists.  similarly, i should note that i am listening mostly to classical and a bit to jazz and, rarely, to pop.
 
i've got a 128gb microsd full of classical music in flac format riding in the player most of the time.  i also carry separately a 64gb card with jazz and pop.  switching from one to the other is a matter of seconds.
 
i listen on either akg k812's or etymotic er4pt's, depending on my need for sound isolation, and those pairings work well.  the sound is wonderful: rich, detailed and immersive, with good separation and tight, clear control across the whole frequency spectrum.  whether listening to a bach violin partita or a brahms symphony, the imaging and reproduction are great.  the dx90 set on high gain was also quite capable of driving the hd700's i no longer have, but produced a smaller soundstage on those 'phones than when they were driven by a more powerful amp.
 
the size and weight are very handy - those specs are widely available and it's easy to compare them with, e.g., the fiio x5, and see how the dx90 is smaller and lighter, easier to tote around. i can't compare sound signatures as i haven't heard the x5.  the dx90's ability to switch batteries means that you never need to run out of power.  it uses widely available galaxy s3 compatible batteries. battery life might be about 5 hours playing from flac level 5, but i've got several spares i carry fully charged, and the whole package is still quite manageable.  [i ranked the battery life high,  because although the play time of a single charged battery is quite limited, the ability to switch in a new battery means no practical limit.]  alternately, some owners use larger batteries, foregoing the metal back-plate and just relying on the supplied silicon case to hold the battery in place.
 
the touch screen is quite sensitive, even with a screen protector, and it took a while for me to develop a light enough touch to move around easily.  this is not a big deal, but was irritating at first.
 
on the whole, i don't hesitate to recommend this player.

i've read a number of reviews around the net which criticize the k812's for harsh treble and limited bass - all i can say is that my experience with these 'phones does NOT bear that out. the bass criticisms appears to come from people who want to listen to dubstep. i don't know what dubstep is. the treble criticisms come from people who are listening to some types of pop music with which, again, i am not familiar.

i am using these phones sourced out of an ibasso dx90   i am listening ONLY to classical and jazz flac files, and the sound is wonderful.

for example, i spent time last night comparing 4 versions of schubert's "death and the maiden" - and the source and phones revealed significant differences among the performances. they revealed not only the obvious ones of tempo, phrasing, and expressiveness, but also differences in how the groups were miked and/or sound mixed/engineered.

the lindsays sounded as if they were recorded while playing in a warehouse, with an open, hollow and slightly distant tone, especially for the cello which sounded a little muffled or veiled. the alban berg quartet and the takacs had a better sound, very clean and present, while the melos recording made me feel like i was sitting amongst the players, and could feel the bows being drawn across the strings. the high notes in the andante movement were intense, expressive and clear- very much revealed by both the source and the headphones, without any sibilance or "tizziness."  in the melos version, the cello was rich and more present throughout in a way that i very much enjoyed.

i then spent an hour or two listening to jazz. charlie haden and pat methany's version of "first song (for ruth)" showed off haden's bass work. the bass notes were deep and rich, the sound of the strings being plucked very clear, while also being tightly controlled without any loose or blubbery sound. the piano on jacky terrason's "nardis" was very much present, not at all recessed or veiled, across the full spectrum of the instrument. some brazilian jazz-pop by maria rita carried the vocals forward. they were lively and caught her occasional slightly gutteral or raspy sounds.
 
through all the music, classical or jazz, the phones presented a spacious soundstage, with good separation of instruments, but with the size of the soundstage varying with the recording.  in the schubert, for example, the lindsays had a 180-210o wide soundstage, while the melos quartet was spread over only 120-150o.

bottom line: i'm very happy with these headphones.  i can't speak to their application for other forms of music, but for what i want to listen to, they're great.
 
edit- to add a note about comfort- i listened for several hours yesterday and there was no fatigue. they're extremely light and comfortable, so much so that i didn't even think to comment on it.

my experience with headphones is very limited, as is this review, but i thought someone might benefit from these observations, someone who wants to listen to classical and jazz.
 
i started with the hd700 by listening to the melos quartet playing schubert's "death and the maiden," and then checked my impressions by playing segments on my fidelio x1.
 
wow!  the hd700 had what felt like a 220-240o soundstage- i was sitting in the center of the quartet. the tone was wonderful and i was surrounded by the music- the first violin to my left, the cello on the right and a bit behind me, the viola front left and the 2nd violin front right.  the last 2 were a little hard to separate, especially because they were often playing in unison, but then i could hear snatches of their playing that i had never noticed before, and which placed each of them clearly.
 
the x1 in comparison had about a 120o soundstage, with the instruments much less clearly demarcated. the x1 placed the instruments at a bit of a distance, in front of me, perhaps 10 feet in front of me, not around me.  also i had thought the x1 was incredibly comfortable; the hd700 is significantly more comfortable.
 
i tried some orchestral music with mendelssohn's midsummer night's dream [previn and the lso] and the contrast between the 2 headphones was the same.  i did think i caught a little bit of sibilance in the hd700 on some very high, bright, moments in the overture- cymbals? i'm not sure, but it was just a moment or two, and worth the price for the rest of what i heard.  then some chopin, some bach.  with solo instruments the contrast was less soundstage than air- the spaciousness of the hd700 and the richer tone it produced.
 
the x1 is a bit warmer, and i'd expected it would provide the better bass, but i was wrong.  it was warmer, but the bass on the hd700 was richer and clearer.
 
time for jazz:  i started with antonio carlos jobim and elis regina- i suddenly got confused about what set i was wearing- the fidelios felt a LOT more open than they had with the classical pieces.  i think that the recording had a lot more channel separation, which the x1 used to good effect.  nonetheless, the hd700 were in another class- richer, more immersive sound.
 
of course they SHOULD be in another class: they cost 3 times as much.
 
i stopped bothering to switch back and forth. i didn't need any more convincing.  art farmer; bud powell; branford marsalis; charlie hayden and pat metheny; chet baker and paul bley.; the clayton brothers [and that only got me to "c"]...   my head was bobbing and my feet tapping in a way they haven't for a long time.  
 
my "normal" sound system uses flac files streamed from a vortexbox to a squeezebox touch, then optical to a gungnir dac, then cable to a nad c375bee amp, then to kef iq9 floorstanding speakers.   i think i've got a pretty good system, not ultra-audiophile, but good. i was listening to the headphones from the phones outlet of the nad amp.
 

the hd700 is better than my "normal" sound system.  it was a bit of a shock to realize that, but my "normal"system can't hold a candle to listening with the hd700.  i can't imagine what i'd have to spend to get a speaker system that sounded as good, as rich, as immersive, as these headphones.  [not counting putting an addition on my house for the listening room.]
 
so i'm impressed and enormously pleased by the hd700.  for what i listen to - classical music and acoustic jazz- they are wonderful.  
 
 
edit: the hd700 is also relatively easy to drive.  it was louder than the x1 with volume set the same on my amp.  i just got a fiio x5 that i'm hoping will be able to drive the hd700.  i'll post the results here when i get around to actually checking.