I haven't heard the Audigy, but from what I've read the Pwave is
at least as good. You could get a receiver for $200, but with the Powerwave you don't need one: it combines the functions of a soundcard with an 15 WPC amp module. It accepts USB right from the PC, although it has line/mini jack input, too. It can even work as a mic preamp and makes a good 'phone amp.
If you go that route, you connect the Axioms to the Griffin, then the Griffin to your PC. You then use whatever media player to control volume, etc (you can simply use Windows Media Player if you like). That's how I've got my PC sound set up, and I'm very happy. The whole unit is about the size of 2 or 3 CD jewel boxes stacked up and weighs about as much as a couple packs of smokes.
If you're interested you can read more about the Griffin
here. It's sort of marketed to Mac users, but it works perfectly with windows/Intel/AMD machines, too.