I have an Audigy2 ZS and Logitech Z-640 speakers...GREAT combination. Plus it has an adapter to let you hook it up to a DVD/VHS player with RCA audio connectors (just plug in the wires and press the matrix button on the center speaker).
You can buy wire extensions at Radio Shack for a few bucks a pop - my brother has a z-640 set hooked up to his TV 24/7, and we bought two 12' extensions for the front r/l speakers, and two 24' extensions for the rear r/l speakers. I think they're just RCA extension cables; they come in gray.
Oh yeah, if you get these or another 5.1 set, be sure to try out the DVD-Audio sampler disc that came with the Audigy2 ZS...the classical music sounds KILLER!
I'd say the z-640s are the best 5.1 $50 speakers available.