PC Audio Basics

I think this question is so basic it is difficult to find the answer.

I am looking to set up a home theater pc with an emphasis on being a music server with very good quality sound. I intend to hook it up to pair of good quality speakers like the Rega r3's. The PC is likely going to be a mac mini running vista.

My question is what do I need between my PC an the speakers?

Do I only need a DAC and can use foobar at the pre-amp?

Do I need a separate amp? If so, can an amp serve as a DAC as well?

Thanks for the help.