I bought the 497s for $75 and the 515s for $100. They were bought retail though, which is usually more expensive than buying online. But it let me immediately evaluate them... I was able to buy the 497, return the 497, and buy the 515 all in the same day, and I could buy/return more today if I cared to. Even if I stick with the 515s, I could return them and buy them cheaper online... buying retail is thus a great way to evaluate things, though their stock is limited of course. But CompUSA had the Stenn 202s, 515, 497s, 457, and PCX-250, quite a good selection relatively speaking. And Circuit City has the 212 Pro.
After using the 515s more, I have to say I doubt I'll find a more comfortable headphone... as headphones go, you can't really get more comfortable than this. But the sound is definitely worse than the 497s... it seems muddy.
I've read alot of reviews, but the problem is I've read barely any reviews from gamers. Surround-sound is another important consideration for me, but it's useless for music and not very useful for DVDs. It's extremely important in games though, because you're actually in a game, with things going on all around you -- you're not merely watching it.
Oh, and keeping in mind that I've never used headphones before... it's very obvious, with both the 497s and 515s, that the sound is coming from right outside your ears. I assume this is true of all affordable headphones? (Ignoring ear-canal 'phones.)