350SE is stereo, unless you use them with a sound card providing 'virtual' 5.1/7.1 as some people like to call it. 363D comes with it's own USB sound device that does the same thing. 363D is the USB equivalent of the 360.
Tiamat uses multiple drivers, like the Roccat Kave, and they are labelled as 'true 5.1/7.1'. 'True' is just a label used by companies to sell their multi driver headsets. Stereo + Dolby Headphone (headphones+sound card or 363D) is labelled as 'virtual' to make that way of getting surround sound though a headset/headphones, sound inferior. Marketing sells products, so plenty of gamers go for the 'true' option. Some people prefer multi driver headsets, where as some people prefer the simulated or 'virtual' approach. All that really matters is what works for the individual.
