Lot's of great info guys thanks a lot :)
LOL, I used to own one of those M-Stage's and was the person who first suggested doing the Class A op-amp mod on it. The OPA627 with small bias current or LM4562 pushed hard should warm things up more than the stock OPA2132 (which sounds a little etched and grainy in that amp.) The M-Stage's transparency, bass control, and treble extension is great for its price; but the one and only reason I wouldn't recommend the M-Stage is that it lacks dynamics and SLAM, which the HD800s need to avoid sounding anemic. But if the OP is already happy with the HD800's bass, the M-Stage is certainly a good value.
For most listening purposes I'm happy with the HD800's bass. There's the occasion when I want a little more oomph (trance, house etc).. but could that be sufficiently done with an EQ? I haven't had any problems using the HD800's with Logic 9 for producing purposes and so I think I'll stick with them.. with the exception being for DIY vocal work, I think they're fantastic for this purpose. Some may prefer to use multiple headphones for different reasons, but if I stick with the same set for both leisure and creating I think the overall effect will be a better balance in the sound, because I will know that "these headphones emphasize this frequency or that frequency" and can adjust accordingly. At least that's my hope! Anyone agree? Disagree?
Oh and I'll definitely be looking into the Matrix M-Stage as well as the Nuforce HDP. I'm leaning toward the M-Stage because of the lower price but it'll be some time before I can purchase. May as well do some research in the meantime.
Edited by Entranced - 8/13/11 at 8:35pm