A pair of 5850's needs about 20 amps (well, 18 amps to 24 amps peak). The CPU needs about 10 amps. Overclocking will add up to 20% to that figure.
A good 650 watt PSU will work, but I think it would be kind of close. A good (Seasonic, Corsair, Antec, or XFX) 750 watt PSU would be better.
what about 720W "Gigabyte" ODIN Power Supply
720W "Gigabyte" ODIN Power Supply
720W "Gigabyte" Superb Power Supply 120mm fan low noise silent design with Auto fan speed control 1x 24-pin Motherboard Connector 1x 4+4-pin +12V CPU Connector 2x PCI-E 2.0 (6+2) Pin Connector 4x 4-pin Peripheral Connectors 7x SATA Power Connectors 1x 4-pin Floppy Connector Complies to INTEL +12V 2.3 regulations Active PFC, high efficiency power circuit design, 80+ certified, 3-rail, 12V+ design Over-voltage, over-current, under-voltage and short - circuit protection Reliable Japan-made main capacitor Environment friendly, Complying with RoHS & WEEE regulations PCI-E 2.0 Support With sleeved cable for better cooling performance SLI certified.
is gigabyte PSU a good enough brand?
750W "SilverStone" ST75EF Power Supply