i'll admit that i'm unfamiliar with the tech or specs behind 5.1 headphones. i usually recommend discrete speakers, since you can get a decent set of logi 5.1s for around the same price or less than you'd be paying for these headphones. wiring can be an issue, though.
i know little about this technology, but as far as i can see i'd avoid CMSS-3D if possible. there's only a few cards that support it, and they're all X-Fi (aka, notoriously incompatible, with sloppy drivers and poopy support). dolby's likely a better route.
tbh, a set with integrated processing would be a better choice, as far as i can see. it'd be nice to get a good sound card and then have nice cans, but that'll cost more in the long run and you'll have fewer issues getting the sound card to work with your system.
if you're just asking about what sound card is best that's available nowadays, i'm only intimately familiar with one - the Soundblaster Live! 24-bit usb card. i liked it, a lot. don't use it now because it conflicts with some drivers for my recording interface. when i divorce gaming and music onto different computers, i'm going to reinstall it and pray that the drivers still work on w7.