500 Watt or greater power supply with 2x 75W 6-pin PCI Express power connector recommended (600 Watt and four 6-pin connectors for ATI CrossFireX Technology in dual mode)
Plus, that PSU has 6 6+2pin power connectors, so it has the capability to run two or even three video cards if you ever need or want it to. It has 70amps on the +12v rail which is enormous.