For my sweet spot being around 1280x1024 and its widescreen equivalent the FPS differences are much more pronounced. getting anywhere between 10-25 fps better on some benchmarks and averaging around 15fps better.
But back to my original question. What are your thoughts on powersupply?
The easiest way to pick a power supply is to get one that is certified for SLI by Nvidia for the card types you will be running. You can do this by going to the link that someone posted earlier in the thread. I don't know the what the 8800GTS requires on the 12v rail, but you can find that out easy enough using Google, then just head over to Newegg or something and check the specs on some psu's and go from there.