The Sennheiser HD555 I ended up getting have been quite excellent! They're very comfortable. I always feel them a little on my head as they have a good bit of clamping force, but they don't touch my ears almost at all. The shape is quite nice, it envelops my ear as it's more rectangular than circular. So at the end of the day, they feel pretty much the same on my head and my ears are very happy. They breathe more than I expected as well. The material is soft and comfortable, though nothing will really compare to velour. Overall I'm quite happy.
Sound quality is pretty good. Balanced overall. Good amount of bass, could use a touch more highs. The soundstage is pretty wide but not overly wide either. I have not yet done the 595 mod and have been running them mostly off of my onboard Realtek. They definitely benefit from going through my Mini^3 and E-MU 0404. Instant increase in clarity, resounding bass difference and well just about everything really. They're not quite as clear as the DT 990s but their clarity is what you would demand from $150 headphones. For metal and dubstep I'm happy with the sound especially since they don't need an amp to sound decent.
I plan to do the foam mod and then possibly remove the inner grill as well to up their sq further.