build the mythtv box
http://www.antec.com/us/productDetails.php?ProdID=15728
Hauppage PVR-350 (comes with a remote)
Whatever hard drive you want
the PVR-350 doesn't require much CPU on the main machine, so, you should be good to go.
And you get the thrill of putting it together yourself.
My nephew will be building mine this summer if I can separate him from his XBox