MSI GTX 580 Lightning PSU

Your psu has the proper pcie connectors.
What's the problem.
Use one 6+2 and a 6pin for each card.

I have been wondering if my XFX - XXX 650 watt PSU could handle a single MSI GTX 580 Lightning. I've read that all I need is a 600 watt PSU in one article and read that the minimum is 700 watts in another article, which is true? I don't plan on overclocking the 580 Lightning until the card starts to have trouble (below 60 fps) with newer games.

Here is the rest of my system if it will help :

Gigabyte 890FXA-UD5 AMD based motherboard
AMD Phenom II 1100T Thuban
G.Skill RipJawz 4gb DDR3 RAM @ 1600
Western Digital Caviar Black 500gb sata3
Western Digital Caviar Black 320gb sata(1?)
ASUS DVD Optical Drive
Cooler Master HAF-932 with 3 200mm fans + 120 mm fan.
BFG 9800 GT Eco Intelligence Edition

(future, summer upgrades)

1 OCZ Vertex 3 240gb
Noctua NH-D14

(just incase I'm cutting it close, I'd like to know if I should upgrade to a 750 watt or a 800 watt PSU)