Here is the Hannibal PVR, a media center PC packed with features that costs only $550. It uses myth TV and has native 1080i output, is wireless out of the box, can rip DVDs, has built in torrent support, has 7.1 Dolby support, and can supposedly play any media format.You can see a full list of features listed here, you may quickly notice there is one very important thing missing, a TV tuner card.
So unfortunately this PVR is not ready to run, but according to a post on Digg you can just drop your chosen TV tuner card in and be ready to go.
