All this K701 talk makes me want to give them a couple more listens. I've only heard stock K701 and balanced HD800, and they sound waaay different, mostly in the bass. I think the AKG is missing some midbass and is too relaxed or airy or something. The best adjective I can come up with is "weak." The balanced Senns, though, have all the bass I need, and I'm a borderline basshead.
I wonder if it's as simple as a balanced drive issue. Or maybe the HD800 has problems fitting some people's heads?