You probably want to try the optical connection and use the dac in the receiver since computers tend to be acoustically noisy environments. The audio engine P-4s aren't cheap at $250 but they are really good set of speakers for a desktop,
http://audioengineusa.com/Store/Audioengine-P4. They're small, they sound great, and they are front ported which is, I think, a plus for a desktop, nearfield environment.