Thanks for the replies. I'm still researching my options. While the Tritton PC510 HDA defintely sounds like an amazing product I'm a bit unsure about whether any true 5.1 headset can accurately provide a surround sound experience given how close the drivers are to each other. I would absolutely love to hear anyone's experiences with surround sound with a true 5.1 (or 7.1) headset. Did it actuall yprovide you with a compelling surround sound experience?
Also, are there enough games out there that support it to warrant the expense?
I'm beginning to think that I may just forego surround sound altogether and get a quality stereo headset. My girlfriend has an outstanding pair of VModa Crossfade LPs that not only sound amazing, they are also beautiful, very solidly built, have a mic and includes a case for the same price.
A stereo headset also has the benefit of being usable with my consoles (through the television), iPod, DS and PSP whereas the Tritton PC510 HDA would be usable only with my PC.
I've never personally heard a 5.1 or 7.1 headphone, but I can't imagine they're good. Multiple drivers present many problems, all of which are greatly exacerbated in such an enclosed space. The sense of direction and space in audio is created by the interaction between sound waves and your outer ear, by specific kinds of delay and equalization between channels. Multiple drivers in an enclosed cup an inch from your ear isn't going to allow for any of that. So ultimately the best sense of surround sound in headphones will come from software regardless.
As for specific stereo headphone recommendations, you might try to pick up a pair of http://www.amazon.com/Creative-EF0060-Aurvana-Live-Headphones/dp/B000ZJZ7OA/ref=sr_1_1?ie=UTF8&qid=1328821081&sr=8-1 headphones from Amazon. They go on sale for $60 a lot. They'd be more useful with your iPod than other recommendations I'd give, like Audio-Technica AD700 or Sennheiser HD555/558, which are open-back and leak sound in and out. If you really want to cheap out you can get a pair of http://www.amazon.com/Koss-KSC75-Portable-Stereophone-Headphones/dp/B0006B486K/ref=sr_1_1?s=electronics&ie=UTF8&qid=1328821294&sr=1-1, which are very portable and very good for the money. I've used them briefly for gaming and they work quite well. They're the best bargain I can think of for any kind of audio.
Then with all the money you save buying a good pair of stereo headphones, you can get an http://www.amazon.com/ASUS-Xonar-Sound-Cards-XONAR_U3/dp/B0054L8GVK/ref=sr_1_1?s=electronics&ie=UTF8&qid=1328821336&sr=1-1 or equip your computer with a http://www.amazon.com/ASUS-Channel-Sound-Card-XONAR_DG/dp/B0045JHJSS/ref=sr_1_2?s=electronics&ie=UTF8&qid=1328821336&sr=1-2. I know some people don't like Dolby Headphone as much as Creative's CMSS-3D, but it works well for me.
http://www.head-fi.org/t/534479/mad-lust-envys-headphone-gaming-guide-all-testing-w-dolby-headphone-updated-2-6-2012 for more good recommendations of all price ranges.