I currently own a radeon 9800pro and a GeForce TI4200. They have all the same connectors DVI, S-video, and VGA. Both cards are 128 MB ram. What's the best way to get the playback to my TV? Keep in mind if there is a better video card I will get it but it will need to be AGP.

The GeForce Ti4200 should be the easiest to get working. This (slightly out of date) wiki page has more. http://www.knoppmythwiki.org/index.php?page=VideoCards

I'm probably asking the wrong question here. I think what I really want to know is.... I've setup my Mythbox. well sort of. I have video from my ATI 9800pro. The thing is the display on the screen when showing programming doesn't use the whole screen. I guess I'm not sure if that's just the way it is or if I need to do more configuring. I also have no sound yet but that may be another post after I deal with this issue.

I forgot to add that the SD channels don't tune in either. I'm not sure what the deal is with that.

Ah. Search for "overscan", here and on the wiki (there may even be an overscan how-to there). How you set it up is different for ATI and Nvidia, and there was someone recently who had issues enabling it for ATI cards. With Nvidia you can just use the "nvidia-settings" utility to tweek it to the right size.