If you're looking for some ideas for your own Media Center system, you might find some inspiration by reading this system building guide
The guys in the Corsair labs have set themselves the challenge of making a silent, powerful box that will handle MCE with aplomb. Included in the rig is a Pentium D chip to handle MCE's many requirements (TV, music, video simultaneously) and a hefty 2GB of DDR2 RAM to prevent the system crawling to a halt with all that going on.
Included in the guide are some useful ideas as to components and cooling methods, with the lab rats choosing a Thermalright XP-90 heatsink to interface with the Pentium D (which, as we all know, is something of a dog to keep cool).
There are also some handy hints as to MCE software installation, which can get hairy if you happen to choose the wrong hardware - the OS is very picky about what it likes to work with.
However, despite using a Pentium chip and 975 mainboard, there is not a Viiv logo in sight! Erk!
Take a look, then let us know your experiences of building systems for PVR over in the forums.