Each 8800GTX needs two 6 pin pci-e power connectors, therefore, you need a psu that has 4 such connectors. A quality unit will be able to drive all 4 connectors, and then some. So, for a simplified filter, just look for a unit with 4 connectors. This will usually be for a 750watt psu. Look for a quality unit fromm corsair, PC P&C, seasonic.