You won't be anywhere near 750W. Maybe 600, but that would only be done if you were folding on both cards and folding on all four cores of the CPU. Remember when your gaming you will only use 1 or 2 of your CPU cores, very rarely is there a game that can use all four cores and come anywhere near 100% load.
That newegg calculator would be more accurate for a lower quality PSU (some tend to be overrated). So the newegg calculator is geared more for the user to be on the safe side.
You should get yourself a P3 Kill-a-watt meter, they're only like $20. Then when you have your system built you can measure exactly what your PC is drawing.
Actually you won't have to buy one because one thing thats not on your list is a UPS (uninterruptable power supply). They protect your PC from power outages and brown outs also power spikes. I'm using the Cyberpower brand, check them out, make sure you get one of the latest version they are more power efficient. They have a LCD readout and can tell you how much power the PC is using.