Pc As A Dvr/pvr/media Player

Hi everybody. Happy new year 2008.
I intend to buy or built a pc desktop to use to record tv shows and movies from my dish receiver or another source and to use to output my music to my receiver. I know that one of the most important piece would be the video card . do you recommend any in particular? how about the sound card? wich would be the best way to go: buying a ready built system or to built it myself?
thank you
frontera