Looking to turn your computer into an entertainment center? You'll need to start with a decent TV tuner card. NeoSeeker has a review of the reasonably priced PowerColor Theater 550Pro. They say:

The PowerColor Theater is 550Pro is a very nice piece of hardware. MSRP is a very reasonable $99 USD and video quality is very good in general although the video seems a bit on the soft side. The filtering algorithms used by ATI seem to be effective the videos have very little noise and color bleeding seems minimal. During testing, I got comments saying that the image on a tired 14" monitor which the test system was set up on looked better than an actual TV (a rear projection Sony widescreen to be exact) from a person who is not technically adept which I think says a lot about the image quality of the 550Pro.

The MPEG2 encoding offload made a huge difference in processor usage and I think that the claims that this will work on a 700 Mhz machine may actually hold up.

You'll want to be sure to look at the nice screen captures on page 5 of the review.

Read the PowerColor Theater 550Pro TV Tuner Review