Fun site to play with Power Supply forecasting. Allows very few settings for overclocked systems but still able to change to higher equivalents for better accuracy. Ie overclocked video card perform similar to next model up...
Try it out and lets make this site a sticky for all those PSU questions we all see:
Notice at the top of the page (flashing in RED letters), at the PSU calculator the required minimum amperage for the +3.3, +5, and +12 volt rails.
http://www.extreme.outervision.com/