Am not sure what everyones setup is but I should elaborate. Using CMSS and other software programs is for turning regular stereo into virtual surround, its not the same as having true 5.1 audio. It also adds reverb and echo effects to your output.
Of course, you need a DVD movie in 5.1 and software/hardware DVD player capable of true 5.1 audio (for movies) or a game that supports EAX 1,2,3,4 or has really good software 5.1 audio (like Doom 3).
I would recommend using the Fiber Optic or Digital Coax to transfer the signal from sound card to speakers. Does the 5.1 Ultra have a digital decoder?
Then you need to change your Windows settings to match your current speaker setup. Other wise you'll have some audio channels not being played properly, even in games. I am currently using a Yamaha Cavit system in 2.1 mode.
http://www.yamahamultimedia.co...ducts/cavit/rpu200.asp
If I decide to add more speakers I can enable them in Windows and then on the reciever itself. I can also turn regular windows stereo sounds and music into vitrual surround directly on the reciever. This generally sounds better and uses less resources than software from Creative. The USB connection is mainly for customizing equalizer settings and adjusting speaker volumes independently.
Does the 5.1 Ultra allow you to upmix/downmix between 2.0, 4.0 and 5.1 audio regardless of your input? It may be worthwhile to mess with the switches/buttons and see what works.
EDIT: You could also look around for a Super Audio CD to experiment with. cduniverse.com has a few.
As far as the Audigy goes, I just use the drivers and ignore the special utilities for audio manipulation. They're nice but not needed. In case anyone was wondering, I have a friend who lets me mess with his Klipsch system. Very nice but I dont want to invest that kind of money yet.