For less than 200 dollars, there's not a lot to complain about here. The MX1's amp sounds quite good and powers K702s without trouble, and the DAC does a respectable job and sounds even better when hooked up to a separate amp.
 
One problem I have with the MX1 is the gain is a little too high. With most of my headphones, I can barely turn the volume control past the 8 o'clock level, which causes some channel imbalance. As a preamp, though, I don't have this problem, probably because my headphone amp allows me to further adjust the volume.
 
I fully recommend the MX1 as a convenient, one-piece solution to get great sound out of a computer. Although it's not the last word in sound quality, as a solid-state DAC/headphone amp combo, it's hard to beat in terms of value.

I have had this amp for a few months, and I really enjoy it.
 
The Caliente (and the KICAS as well, I suppose)  feels like a quality product, which it is. It's true that the amp looks quite bland, but I think it's a nice, "no BS" design that just sits there and does its job. The volume knob turns nice and smooth, and the power switch "clicks" nicely. The housing has a very unified appearance, and feels bulletproof. The amp is powerful enough to drive any conventional headphone.
 
The sound is what really sets this amp apart, though. The Caliente adds a layer of depth and realism to the soundstage. But by far, the most noteworthy feature of this amp is the powerful bass, which is delivered with aplomb and hits hard. The warm sound signature complements my K702s nicely, preventing them from sounding too thin while preserving their detail and clarity. As for the middle frequencies, guitars and vocals have a natural tone, never sounding cold. Highs are not overshadowed either, and come across clear and crisp. Keep in mind that although it has a bit of a bass boost, the Caliente's coloration is not overbearing at all; I never thought the sound was too warm with any of my headphones. That being said, though, I don't have any notoriously bassy headphones, nor am I a basshead.
 
Despite the recent arrival of several strong-performing amps from South Korea and China, I believe the Caliente can ably compete among them, as an amp for listeners who want a slightly warm sound. The bass showed some bloom at times, but it's excusable at this price point. Unlike some desktop amps, the Caliente only gets slightly warm after an hour or so. Also, Oriel is a great guy to do business with; he's courteous and responds quickly. At the price their amps are going for now, Purity Audio should definitely be on the shortlist for people looking for an amp for a few hundred dollars. The Caliente was a good value for $400, but it's a steal for $229. Note that since Purity Audio is a Canadian company, the prices are all in Canadian dollars.

Fit and finish

The PS200 fits well in my ear canals, although the body is on the large side. Because of this, they constantly push against my antitragus, making it sore after a while. However, I doubt this will happen to other users. Isolation is quite good; they isolate about as well as my ER6s, despite using single-flange tips. However, the tips are quite thick, and don't squish down quite as easily as the ones supplied with my other earphones. I haven't tried Sony's 'hybrid' earpieces, but I would assume those are softer and thinner.

The earphones’ build is no less than what I would expect for $250. The ‘jet engines’ are solid aluminum, and the cable is mostly well relieved, except for the Y junction. However, although it hasn’t caused me trouble, the strain reliefs aren’t molded directly onto the cable. Nonetheless, the cable feels very strong, and is not likely to fray. In addition, the microphonics are very low. With the cord hanging down, I get about as much cable noise as the Monster Turbine, with the cord over my ear.

Sonic impressions

The source I'm using for this review is my NuForce Icon Mobile's DAC, connected by USB to my ThinkPad, with Foobar2000 - not Windows Media Player, of course, which applies some nasty compression. My ever-expanding music collection is, as of now, 100% rock and variants of rock, from Vampire Weekend to Franz Ferdinand to Queens of the Stone Age. Sorry that there's little genre diversity here, but if anyone wants to send me test tracks in other genres they enjoy, I'd be happy to add my impressions with them to this review.

Detail, clarity, separation

I'm quite satisfied with the PS200, as they do exactly what I was looking for, as they manage to combine most of the merits of my other two earphones: more bass while preserving detail and clarity. Details are easy to distinguish and well-resolved, just as much as the ER6s. Instruments playing harmonies in the background are easily distinguishable. I can easily tell exactly which notes pianos are playing, which is no small feat as they’re buried under guitars and vocals. Individual strokes on a drum are each nicely separated as well. No attribute of the music is overemphasized, unless it was mastered accordingly. I haven’t heard the ER4s, which are renowned kings of detail retrieval, but the PS200s are no slouch in this area – actually, they’re very good.

Separation between instruments is also good, and it is easy to pinpoint the source, even during busier sections. That being said, though, I actually think the ER6s have even better separation through an amp. The detail and speed Etymotics produce is simply phenomenal, but it’s not a huge difference that I miss much. Being a balanced-armature earphone, the PS200s’ transient response is very fast; however, it’s not the fastest. While they’re definitely more responsive than the Turbines’ dynamic driver, there are still my ER6s and the breathtakingly fast Klipsch X5s, which I tried at a store. (As for the X5s, though, I believe the PS200s give better sound for the same MSRP as I disliked the X5s’ treble rolloff.)

Soundstage

As other owners have also reported, the PS200s throw a very good soundstage for an IEM. It feels quite wide, not to mention outside of the head, creating more of an atmosphere than the Turbines or the ER6s can muster. Music is less boxed in, with space created between instruments which goes a long way towards making music sound more alive. Although I’m not big on movies, I found that during various clips the broad soundstage really helps improve the experience. However, although the soundstage is wide, its overall depth is somewhat lacking. The PS200s don’t seem to extend to, say, the far reaches of a concert hall.

Frequency response

Moving on to the frequency response, I would say the PS200s are a fairly balanced-sounding earphone overall. That aside, though, they’re quite a forward sounding pair as well.

Starting with the low frequencies, the bass is definitely noticeable, but isn’t over- or underemphasized in any way. In short, it fittingly provides a base for the rest of the music. Several earphones have been described as such, and the PS200s are no exception. That’s not to say the bass response is uninteresting, though; there’s a good deal more than the ER6s for sure, making the ER6s sound piercing and dull. Notwithstanding, the bass is still much lighter than dynamic earphones, although transient response is much faster. If you like hip-hop, don’t get these; the deep beats of hip-hop need slow decay to truly settle in. As for rock, the bass is superb; quick successive bass drum hits, especially those of Neil Peart and Dave Grohl, are easily defined and inuntrusive. The PS200s’ bass detail does not disappoint either; bass guitar is easily discernible, despite being buried under other harmonies. One complaint is that compared to the Turbines, bass instruments and drums have less body and fullness; this is especially noticeable in Rush’s “YYZ,” I might add.

The middle frequencies of the PS200s are quite pronounced compared to other earphones, but nothing like the SE530s, another mids-loving earphone. The former tends to emphasize crispness and edge over the latter’s smoothness. Vocals are a real treat with this earphone, and sound airy and natural, but never forced. The PS200s are not forgiving towards sibilant vocals, despite handling them better than the ER6s. With midrange instruments like guitars more prominent in rock music, the sound is more vivid and active, but can be fatiguing as well. Despite very limited time spent with Grados, I would say they have a fairly similar sound signature – but don’t take that for granted.

The PS200s’ treble definitely has a lot of energy, making cymbals sizzle and hi-hats sparkle. In rock music, there aren’t a lot of instruments in the upper treble, which is mostly dominated by percussion. However, I feel the treble definition is especially good at this price point. This, and treble extension, are where the Turbines suffer the most. They sound dead and bloated compared to the PS200s. In addition, the treble is much better controlled. Whereas the ER6s had a tendency to ‘spike’ the treble at odd points, creating what I can only describe as aural pinpricks, the PS200s do not. Everything sounds very accurate and true to the music. I should add that the PS200s prioritize the snap of percussion over the succeeding resonance, some may not like.

I especially enjoy Vampire Weekend, Rush, and the Hush Sound with the PS200s. This review might be somewhat biased because I only used rock music, so those of you reading this, please don’t hesitate to send me other genres.

Overall, I believe Phiaton has hit the nail on the head with the PS200s. I haven’t heard any more expensive IEMs, but notwithstanding, there’s nothing the PS200s really do wrong, and a lot of things they do right.