I have roughly the same experience using the HD800 amped. Of course, the sound will vary according to the type of music, whether it's low-fi garage punk or hi-fi pop or classical...but the sound is still shockingly good. And it's my good fortune that I get this kind of sound through an iMac, using iTunes with Sound Enhancer to increase the stereo separation.
The sound is just "right." I realize that some have found the HD800 a little picky - but I guess I just lucked out with the synergy on my system. I know that because the same synergy isn't there when I listen to the same music using my stereo system.
I don't think the HD800 is picky, I think the people that listen to it are picky