I’d start by checking the minimum and recommended requirements for a system using the Ceton card as posted on the Ceton website. I believe the recommended RAM for extenders is about 500MB per extender. 2-3GB should be sufficient. The PSU depends on what else you’ll be stuffing into the case. Here’s a comprehensive list of recommended components for building an HD HTPC:
http://www.avsforum.com/avs-vb/showthread.php?t=940972
Follow the most current link for the latest updated list of components as many of the older ones are no longer available.
