Do not get an actual surround sound headset, they achieve their surround sound by sticking crappy speakers into one can to achieve surround sound, are in reality very terrible and actually worse at positioning sound than a hi-fi dual channel headphone system. If you want surround sound on headphones then your best bet would be to go for a good pair of headphones (Audio Technica AD700s are renowned for their performance for the dollar regarding sound positioning in games). Anyway, if you want another pair and not the $95 Audio Technicas, just keep in mind that for gaming you will need to look for a pair of headphones that is known for positioning audio well, usually this will lead to towards brands like AKG, Audio Technica, and Sennheiser that have wonderful sound positioning. Someheadphones will also perform like miracles with headphone amps, it sometimes better to get a cheaper (decent) pair of headphones and and amp instead of just splurging all your cash on the headphones, at your price range though I recommend you get a pair that perform well amped and unamped (once again, the AD700s fit this). Also, if you're worried about not having "true" surround sound, keep in mind that you can get something such as the astro mixamp or a sound card that can virtualize surround sound (this is really the only way to get anything close to a surround sound speaker system with headphones, and actually is sometimes better). You would be looking for devices with Dolby Headphone or something similar like Creative's CMSS3D on their sound cards. Also keep in mind that more expensive does not necessarily mean that it's better for you.
If you want more advice, i suggest you head over to the
head-fi forums, they know their shit there.