Power Supply Requirement for Nividia GTX 460 SLI

[PablosPandas]

Hello everyone I had a question about whether my power supply was enough to run two GTX 460s in sli.
My power supply is the Rosewill CAPSTONE Series 650W Continuous @ 50°C, 80 PLUS GOLD Certified
http://www.newegg.com/Product/Product.aspx?Item=N82E16817182071
Is this enough? Can I overclock both cards or only one? Or none? I know it has a single 12v rail at about 52 or 54 amps which was rated as 648w

My other pc specs:
CPU: i5 2500k (Not overclocked yet, might oc to 4 ghz but I will see how the system performs)
Motherboard: GIGABYTE GA-Z68X-UD3H-B3 LGA 1155 Intel Z68 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard
Ram: G.SKILL Ripjaws Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL9D-8GBRL
HDD: Toshiba 500GB 7200rpm
VGA: GTX 460
Standard disk drive
Windows 7 64 bit
Case: Rosewill Challenger mid tower gaming case (Took me forever to get the psu screwed into the case since there were two holes next to each other that were pushed towards the middle.

That`s about it. Any suggestions (On the power supply)

 

[PablosPandas]

kk thanks I had read that 650w would be good but I just wanted to check so I will probably get that power supply.

 

[PablosPandas]

Best answer selected by pablospandas.