I missed all the discussion lol
Personally I think the HD600 is a very pleasant option, comparing around with other headphones I heard. Doesn't burn the wallet too bad, and works pretty well with almost anything IMO.
Yes I have heard the HD800, easily the best headphone I have heard (a tad better than the AKG K812 and Audeze LCD-X), but the price puts me off.
I don't have the urge to upgrade though, maybe cause going upwards is way too expensive for me LOL