Let me start off by saying that I purchased my TH-900s from an authorized dealer for $1,300 brand new (which I still feel is a bit above their true value) about one month ago.  I have owned (and sold) several pairs of D7000s already, so after reading many reviews claiming the TH900 to be an upgrade over the D7Ks in pretty much every way I decided to buy a pair.  My first impression was that they sounded very similar, but there are actually some serious differences.  It's worth noting that I went into this situation with a bit of bias.  I really, really expected to love the Th-900s.
 
These are without a doubt the nicest looking pair of headphones (well, in my opinion) that I have EVER seen.  The cups are just absolutely beautiful.  The pads are a total improvement over the old D7K pads (softer, deeper, they even look a bit nicer).  The cable I consider to be a bit of an issue (just like the D7Ks).  It's non-detachable and 10ft long, terminated in a 1/4" plug.  The wooden stand they ship with these is a nice thought, but kind of a waste if you ask me.  It looks and feels cheap, I would have rather had a nice storage box (the one included with the Th-900s isn't quite as nice as the one that came with the old Denon line).
 
Bass:  Bass on the TH-900s is a bit more extended than the D7Ks, but lacks the overall impact of the D7Ks due to it's lack of overall weight.  Bass is clean, crisp and well defined with the Th-900s, however it's only a slight improvement on the Denons.  Some people may prefer the overall weight/impact of the D7Ks bass to the Th-900s slightly better defined bass.
 
Treble:  I have occasionally been bothered by the agressive treble presentation of the D7Ks.  I sometimes find it a bit too harsh or sharp sounding to my ears, not always but occasionally it bothers me.  The Th-900s improve upon the D7K's treble presentation in every single way.  It is detailed, crisp and possibly the best I have heard from any headphone to date.
 
Mids:  This is where the Th-900s lost me, and where the D7Ks proved to be my preference.  The mids on the D7Ks are slightly recessed.  I was expecting somewhat of an improvement on the TH-900s.  Well, it turns out that it's quite the opposite.  The TH-900s have an even more recessed midrange than the D7Ks do, vocals can sound a bit distant, muffled and just bad overall (well, at least for a headphone in this price range).  This makes the TH-900s sound a bit strange to me, their overall presentation just doesn't sound natural in any way.  The D7Ks do have a typical V-shaped sound signature, but it works well for them as they are still decently balanced overall.  I feel like every aspect of the sound compliments another and they sound truly euphonic.  The Th-900s do make some improvements on the D7Ks, but aren't as enjoyable of a listen overall. 
 
The pricing concerns me a bit too. I feel like these would be an appropriate follow up to the D7Ks at a similar price (<$1000) but are outdone by quite a few options well below their current asking price.  I purchased mine at $1,300 (USD) and I don't feel like they're worth that.  If I were a buyer who purchased a pair at the original price of $2,000 I would feel a bit betrayed or misled after seeing the recent price drop.
 
Overall these are a pretty good sounding pair of headphones but not worth their asking price in my opinion, especially considering all of the other options.

I've owned two of these now and it's time to write a review.  One I bought new last year (and sold on here) and one I bought used on these forums.  To put it simply, this is the best portable headphone amp I have ever owned or heard.  I used this with a pair of Hd800s, balanced D7000s and LCD-2s.  It easily powered all of these with authority.  There are multiple gain settings as well, for more sensitive headphones, although you have to take the amp apart to change this.  The little opamp kit this comes with is pretty cool as well, its really quick and easy to swap them out and fun to play around with different options.  Sound from this amp (stock) is pretty neutral.  I did many comparisons with this and my Schiit Lyr (out of the single ended output from the PB2) and I can honestly say that I could not tell them apart, this little amp can really power anything with some serious force!  My one and only complaint is the ridiculously low battery life of this amp.  I would say based on my experience that this amp has a realistic battery life of 5-6 hours when fully charged.  But I guess that's a small inconvenience for such an awesome amp!

I recently spent about a month with a pair of HD800s.  I was immediately more impressed with these upon my first listen than with any pair of headphones ever.  The amound of detail these present is just unreal.  The sound is VERY neutral, true to the recording, and because of this bass can seem a bit lacking.  To be honest, even with bass-heavy music these are a bit lacking.  However they have the fastest, most detailed response I have ever heard from a pair of headphones.  Midrange and highs are the best I have ever heard on any headphone without a doubt.  Soundstage is quite expansive, they sound very "open" and airy with outstanding clarity.  They are hands down the most comfortable headphones I have ever worn.  My one complaint with the design is how easily the paint chips, as many have said before.  They are expensive, and I while I feel that they beat my LCD-2's in every single way possible I still prefer my D7000s to these.  I guess it just comes down to personal taste.  If you like a robust bass response like I will admit I do, these won't be for you.

I bought a pair of these recently, I'm one of many who took advantage of the $399 deal on these.  I think for the price I paid they are a pretty good deal, but they do have some issues.  They are certainly an attractive pair of headphones.  Cable looks and feels a bit cheap, but the 1/4" plug is quite nice.  To me these sound a lot like my D7000s, although certainly not as good, pretty close overall.  They have robust bass response, although it lacks some extension and can sound a bit muddy at times.  I found the midrange on these not quite as good as others describe, to me it sounded a bit strange.  The highs on these seemed a bit dull to me.  They do have a very "musical" (sorry) sound to them, which is what I find appealing about them.  They are very forgiving of poor recordings and sound pretty good with everything.  I did many side by side comparisons/litens with my Pro 900s.  The 900s have a reputation for having a blurry and recessed midrange, but to me they sounded just a bit more clear/crisp than the W1000s and overall I decided to sell them for that reason, since I only wanted one pair of headphones in this price range.  I must also say as many have before, the headband adjustment, or lack of, is really frustrating.  If you move around too much they move around too, not a fan of this at all.  Overall I would have to say I definitely recommend them for someone looking for a pair of headphones in this price range.

Amazing headphone amp for the price.  Used with my 325is, Pro900s and Q701s.  Great value, drives most headphones incredibly well, even powered my Q701s on the high gain setting with no signs of distortion.   It's a really nice looking headphone amp for the money also, very study with a neat, clean build.  For the price this absolutely can't be beat.

Let me start by saying that these were absolutely beautiful.  Everyone I know who saw them commented on how nice they looked.  My only complaint about the looks would be the re-cable job.  Heat shrink was done unevenly on each side (one side actually had two pieces overlapped over each other and the other side had one that was noticeably shorter).  Now to the sound... not for me.  I have a hard time imagining that anyone would be crazy about these headphones for anything other than the way they look.  They sound muddy as can be, lacking clarity in every way.  The bass is quite bloated and poor quality and I would say that they actually have less bass than some of the headphones I have (Pro 900s, LCD-2s).  I did a side by side comparison with the Pro900s (with one of my friends as well who isn't really into headphones, so totally unbiased) and the Pro900s sounded considerably better in every single way with every single thing thrown at them.  I can't think of one good thing to say about these other than their looks and I really, really wanted to like these. 

A neat little headphone amp.  Bought to use with my Pro900s.  Definitely intensifies the v-shaped sound signature of these headphones.  Sounds exactly as I expected it to, lots of fun to listen to!  The gain/volume adjustment is the single worst I have EVER used on ANY product however, just absolutely terrible.  Other than that this is a neat little amp for a cheap price. 

This thing does what it's supposed to do and does it well.  Noticeable improvement in sound quality.  For $200 you can't go wrong.  No real complaints from me about the V-link at all.

I was a bit skeptical about a cable actually improving the sound of my headphones, but I bought this to check it out (and because it looks so nice).  I actually did notice an improvement in sound, it seems to open the headphones up quite a bit.  Bass sounds more full, treble more clear and midrange more prominent.  This thing looks ridiculously beautiful, a true work of art.

Really good sounding headphone with incredible bass.  I owned these for about six months.  They sound powerful for lack of a better word.  Definitely a V-shaped sound signature.  The bass can be a bit much sometimes, a bit sloppy, but I usually find it quite enjoyable.  Just a really fun headphone to listen to.  That being said I don't feel that they quite compare to some of the other $1000 offerings from competitors (in terms of overall sound quality) or really outperform less expensive models by that much (Pro900, He-400, dt990 for example).  I also didn't care for the headband, the earcups always slid when I didn't want them to and I've read a few stories of the cups falling off at the hinge, which I don't find hard to believe since it's attached by one small screw.  Overall I enjoyed these, but I do prefer a "colored" sound signature.  These certainly aren't neutral, but a very fun listen.

I've had these for a couple of years now (although they don't get as much playing time anymore) so I figured I'd write a review.  Of all of the headphones I have owned these are the ones that wowed me the most upon my first listen.  The bass on these is just ridiculous.  They are easily driven by an iPod/Phone but do sound a good bit better when paired with a nice amp.  Like many others have said these do best with electronic music, or anything aggressive, however I have found that they perform more than adequately with all genres of music.  They are a very clean and sharp sounding headphone.  My main complaint about these would be comfort, they clamp very tightly and it can get uncomfortable after a while.