Got and installed D5000 wood cups on my D2000. I used the method where you cut off the stands off the plastic frame instead of drilling into the wood. The plastic stands are cut down so that they are level with the rest of the plate. Regarding the cups, the edge where the wood and the plastic meet is actually mainly sealed except for two slots around where two screws from the gimbal? come through on each side of the metal frame. From what I understand, in terms of sound quality, the main difference is the wooden cups. The cable and other parts are a little different as well, but I don't know if they would truly make any significant difference.
The D2000 I found sounded quite bright and kind of distant/hollow and grainy, but the soundstage and overall exciting sound signature (from subbass to sparkling treble) was addicting. Listening to some concert/live recordings were quite good. Bass was not very present for me except for in the quietest of environments, so I will assume that the D2000 I have is one of the earlier ones. I really wanted to like them, but I couldn't wear them for long periods of time so they stayed on my desk for a lot of the time.
The D5000 cups add warmth, a bit of bass and authority. They sound less spacious than the D2000, but also less hollow/odd sounding. The "added warmth" part is important. They now can be relaxing to listen to. I'm not hearing the treble peak that people have mentioned about the D5000, so I will consider myself lucky.
I also have an ATH-W1000X which I haven't used much recently. Treble and mids tend seem sound a bit more crisp/metallic than the D2000 (with D5000 cups), but more easily fatiguing (in relative terms). The extra crispness can be a good and a bad thing depending on the music. Bass doesn't extend as low and is slightly less punchy. Curiously the mids sound more sucked out of the W1000X compared to the D2000 (with D5000 cups). Not sure if I'm supposed to be listening to the W1000X louder, but that can make it more fatiguing. The W1000X has a sound that seems to "take over more space" - wider soundstage?, but the D2000/5000 sounds more relaxed and natural and more spacious. The W1000X is perhaps a bit more hazy sounding sort of in the middle of the D2000 and D5000 in some ways to me, however minus the sub-bass for one. They used to be my main headphones. That was a while back, but the only thing I really missed from them at the time was a lack of the lowest sub-bass rumble which the D2000 and that Denon/Foster series of headphones have.
Anyway, I am super excited about what I've done with my D2000. They've gone from nearly unusable (to me) to definitely worth it.
Edited by namaiki - 8/2/13 at 5:58pm