Evga gtx 580 -Requirements
Minimum of a 600 Watt power supply.
(Minimum recommended power supply with +12 Volt current rating of 42 Amps.)
EVGA GTX 550 TI - Requirements
Minimum of a 400 Watt power supply.
(Minimum recommended power supply with +12 Volt current rating of 24 Amps.)
pretty sure everything i've read was saying you need a high quality 1000 wat PSU atleast to SLI the 580's.
not sure if the info i put in is going to be there but, if you input the info, even asus reccomends 1000 watts.