Hi Outofspace;
I completely sympathize with your predicament.
One thing to consider is the speaker electronics.
Before I got my wonderful Logitech Z-680 5.1 speaker system, I was hooking up individual speakers to my Creative Audigy sound card (analog hookup) and
ALWAYS had a problem getting all 6 of the speakers to fire all the time. The center channel was a particular problem and sometimes the rear channels would not fire. It made a difference as to what the sound source was... mono, stereo, Dolby, DTS, etc.
After installing the Logitech Z-680's, ALL six speakers always fire without fail. The reason is, the Logitech's have a digital control center box that automatically handles all input formats and no matter what it is, will always produce sound out of all six speakers.
The fact that all six speakers are always producing sound does not necessarily mean that it is the correct sound.
EXAMPLE: When I play a normal two channel stereo CD I now get sound out of all six speakers leading one to think it is 5.1 sound when in fact it is only two channel stereo being fired out of six speakers. However, it sounds MUCH better then having sound out of only two speakers. The effect is wonderful and really opens up two channel sound.
So, it makes a difference if your speakers have an audio digital control center box or not, as to how many speakers produce sound at any given time with any given source.
Without a digital control center box you may end up pulling your hair out trying to get all speakers to fire all the time as I did.
If you ever consider upgrading your computer speakers, I highly recommend you avoid any that do not come with a digital control center box. The digital control center box makes hookup a snap; in my case ONE digital cable from the Audigy's digital output did the trick for me. What a wonderful improvement after fighting a loosing battle for over three years trying to get it all working to my satisfaction.