Several Opteron 144's at 2700MHz, and a 146 at 2810MHz (146 will run 3GHz @ 1.55v vcore).
All using 200w to 220w mATX cases.
One of the systems also has ATi x800 PCIe.
All work 24/7 for HTPC usage, and zero problems or issues.
Power supply must also supply power to sat dish LNB's and DiSEqC motor (through DVB-S PCI card)!