Beyerdynamic MMX-300s.
A lot of this depends on what you're going to use them for. If you use them often enough and listen to a lot of music (FLACs for example) then it is worth forking out the extra, IMO. If it is just for sims/games, then I would go for a normal set.
Remember though, a non-USB set of cans will be dependent on your soundcard. There's no point getting a good set of headphones if you're powering them with a calculator. On another note, I've never found that USB soundcards are as good as dedicated - just something to keep in mind.
Finally, I would always keep clear of "surround sound" headsets, pseudo (digital) or true. My reasoning is that you'll nearly always pay a premium for this but in terms of audio quality you'll usually find that a stereo set at the same price point will sound slightly better. I would even go so far as to say surround sound headsets are a gimmick.