Well, I'm not an audiophile so I can't really comment on the sound quality of my Medusa's. They certainly sound better than any headphones I've ever tried before, but I don't have a very wide range of experience there.
I would agree with soloz2 that stereo headphones are probably the way to go. I disagree that the x-fi's positional simulation thing will be better at creating directional sound, but you could almost certainly get headphones with better sound quality and have passable directional sound for gaming and whatnot.
To be honest, sometimes listening to music with surround sound is annoying... when something is recorded off-balance or one side is louder than the other, etc.
Then again, most digital music is very low quality... Would headphones with incredible sound quality go to waste if you're using them for mp3s and whatnot? I mean, my Medusa's are pretty damn good, just probably not $500 studio sound quality good. Would you really be able to notice a difference if you're mostly listening to music on the computer?
I dunno man, I'm a noob at the sound stuff... But I can tell you that I love my Medusas and I'd recommend them to any gamer. Maybe somebody who is an audiophile and has experience with them and other cans can shine some light on this, as I'm not sure how they stack up against other headphones for sound quality. They're great for movies though
I recall watching Braveheart and hearing horses from behind and thinking "Man, this kicks arse!"