All right, the consensus over here appears to be the Mad Dogz. I'm just hesitant cause it seems really lame to spend $300 on what's essentially a modded Fostex T50-RP, which retails for what, a 100? On the other hand the Hifiman HE-400 caught my eye and despite the criticisms here that one looks like it might be the right choice at $399 and it sounds like it's high-end materials/build.
As far as the Sennheisers, if I were to go for any of their models it would be the 650, but that requires a beefy amp so it's out of the question. The 598/555 and other models appear to be designed for acoustic music and wouldn't work well with what I have my D2000 for (electronic music, house, techno, experimental indie, etc.) - the bass frequencies might be neglected.
So thanks guys for clearing it up. Pretty sure we touched all bases.
Edited by jiggahwhat - 1/14/13 at 9:05pm