What kind of video card should i buy or tv tuner card card for windows media center 2005?

Details: I got this new computer duo core ect. has pci express 16x and it has windows media center 2005 installed. Well the questions I have are if i can just by one video card that will work for me as a tv tuner and all the graphics accel. Im interested in hooking my cable tv to my computer to use it as a dvr which is one of the uses media center 2005 has. I want to record live tv so I know I need some sort of tv tuner as the computer doesnt come with one. I dont want to get off air channels with a tv tuner if I can then great but my main goal is to direct my video feed from my cable provider to the computer and record it and for my computer to have outputs for my hdtv. I need a card that can support hdtv mpeg 2 encoding if possible mpeg4. Any help is appreciated thanks. Question might be a little confusing as I dont know myself what it is I should be looking at