I think what you want is either a Rio Receiver or the Receiver Edition firmware (alpha release) for the Empeg.

http://www.empeg.com/v3alpha/car-v3-RE-alpha8/

I don't know much about either of these, so hopefully someone else will confirm and give more details.

You'll also need to turn your PC into a music server. The notes at the above URL gives more information on ths.