Headphones that simulate 5.1-channel sound have been around for a while, but I haven't seen too many that are said to render 7.1-channel sound, but that's just what Tritton's AXPC cans claim to do. It appears to have the hardware to back it up, though, with four drivers in each ear cup. Since the digital audio bitstream goes right into the phones via USB, it's real surround sound you'll be hearing (assuming that's what your source is), and not just some fancy processed stereo sound.
Extra bonuses for gamers: The microphone will let you scream orders at your comrades or taunt you opponents while you're playing online. It also comes in handy when you need to do a little Skype calling. You can fine-tune the volume of each audio channel, and the AXPC headphones are both PC and Mac compatible. Not bad for $80.