Good audio management program?

[Thermite Paste]

Is there any free program that will let me manage my speakers, like choose which ones are used, and customize levels and everything? I have 5.1 speakers, but i don't have the surround ones hooked up. I'm using nvidias NVMixer right now, but it just doesn't feel customizable enought. A media player that can do this would do too.

Thanks!