What graphics card is compatible with this PC? (Details inside)?

I would say the "All In Wonder" series from ATI/Visiontek would be best for you if you're not gaming but going towards more of a media center. It has the HDTV tuner(video capture) and has the DVI slots(use an DVI-HDMI adapter and then use the audio out from your comp). Listing a price range would be of great use, as there are better cards. Whatever card you get should be a PCI-Express 2.0 x16.