For a system using two Radeon HD 7950 graphics cards in 2-way CrossFireX mode AMD specifies a minimum of an 700 Watt or greater power supply. The power supply should also have a combined +12 Volt continuous current rating of 46 Amps or greater and have at least four 6-pin PCI Express supplementary power connectors.
Total Power Supply Wattage is NOT a crucial factor in power supply selection!!! Total Continuous Amperage Available on the +12V Rail(s) is the most important.
Even a Seasonic M12II-650 Bronze (SS-650AM), with its +12 Volt continuous current rating of 53 Amps and with its four (6+2)-pin PCI Express supplementary power connectors, is more than sufficient to power...