The logitech G35 does not provide surround sound. Its only 2 channels (left and right)
It uses the Dolby Digital algorithm to simulate surround sound. The effect isn't bad but most sound cards and even onboard sound is cappable of using the same Dolby algorithms to convert any 2 channel headphone to 7 channels.
That being said, there are other better 2 channel headphones than the logitech G35. Sennheiser has a great selection.
Any particular Sennheiser models that you recommend? My only thought there is I understand they're usually a little on the pricey side, and I'd say $140 is probably about my limit. I should have said is there anything in that price range that can beat the G35's?