Do I need a new PSU

I am planning to upgrade my computer soon and I currently have a S12 500W. I want to upgrade to a C2D E6700 and two 8800 GTS 640mb . I also have a water pump, two hdds, a couple of fans, and other things. Is this PSU enough or do I need to upgrade to something a bit more powerful? If I do need to upgrade, what quite PSU would be recommended, I have been looking at the seasonic M12 700. Thanks for the help.

Edit:
I tried calculating what I needed from this site http://www.extreme.outervision.com/PSUEngine but they said that I would only need about 450W, but this seems way too low.

2 8800GTS', i suggest the Corsair HX 620 or the M12 700, like what you were looking at.

Thanks for the help

BBQ, I'm ashamed of you. Really, that 500W will be plenty if you want to save money. A GTX SLI setup, then yeah the 620 or the 700 but for the GTS, no way do you need a unit with that much ass.

ahhh conflicting reports, I am now confused.

Any high-quality 500-550w PSU will be fine for that rig. You can spend a bit more for extra power, if you want the security of having some "padding".