FF 182
Don't just judge a psu by its wattage. You need one with plenty of amps on a single 12v rail. You could get away with a good 650w psu, but just for a bit more headroom this is a good psu http://www.scan.co.uk/products/750w...us-bronze-sli-crossfire-eps-12v-quiet-fan-atx. Made by seasonic, its a quality psu.
Also have a look here: http://www.overclock.net/t/183810/faq-recommended-power-supplies
Also have a look here: http://www.overclock.net/t/183810/faq-recommended-power-supplies