I find that the MAC is just all around better when it comes to dishing out the music. The MAC mini has an optical output that is fantastic and plugged into a good DAC is all you need. Also the Transporter is a nice solution.
I tried using a PC/XP with an M-Audio audiophile192 card using s/pif out to my MDA1000 but it sound was dull and did not sound right. I have never heard a PC sound really really good and I don't know why I really wonder about the Microsoft O/S and drivers.