I'm going to use one as a router (pfsense) and one as a NAS (FreeNAS).
Neither of these applications should take a lot of power, so I'm interested in using the system in the coolest, most efficient, and most stable configuration I can. I want these things to run for 20 years.
What socket 478 CPU gives me the best shot at this situation? Should I downclock an existing processor? Does the FSB play a part in heat/power and should I run it slow (400 mhz).