CMSS-3D is only fractionally poorer than true 5.1 either your character or the sound source is moving. If both are still, the stereo can't accurately reproduce the sound as well as 5.1, but to be honest this is rare.
I really need to try this CMSS-3D thing, is there a site where I can try it? Or does it require a Soundblaster Card to use? I really want to see how it compares to a "real" surround sound headset like Psyko, I've actually taken on an xtra job so I can afford a pair of these, but still not sure it would be a good move. "Mad they called me, MAAADD!! (twitch) Ha Ha Ha,,, I'll show them Mad"
I found this revew on a number of SS headsets, including the Psyko http://www.tomsguide.com/us/Surround-Sound-Headsets,review-1357-7.html
I'm not personally convinced by the effectiveness of CMSS-3D effects. I use an x-fi extreme music card with the PC350's and have CMSS-3D turned off for gaming. I still find the positional audio great for online first person shooters. Enabling CMSS-3D just seems to affect the clarity of the audio, to my ears at least.
After looking it up I found a pic I also found this description "The headset's surround sound hardware is built right into the included USB adapter, which plugs into any USB port on your PC or Mac with no additional software necessary. Simply plug the headset in to the USB adapter, and you're ready to go. The one-touch on/off switch allows you to turn surround sound on or off, and the USB adapter emits a cool, blue light to let you know when it's on." Looks like the headsets surround sound depends on a USB device, I don't think than can run from a sound card, but I’m not sure. Anyone able to finalise a yes or no on that one?