My personal favorite pg platform at this time is one based on a 2 socket, dual core ready mainboard with 16 DIMM slots combined with dual core AMD Kx's.
Right. We've been buying Tyan bare-bones boxes like this. It's better to go with bare-bones than building boxes from bare metal because the cooling issues are addressed correctly. Note that if you need a large number of machines, then Intel Core Duo may give the best overall price/performance because they're cheaper to run and cool.