[EDIT] I'm not sure if this helps, but I'll probably end up installing some Cathode Tubes and LED's and stuff like that.
[EDIT #2]: Here's the build, if anyone would like to take a look. (unfinished, still looking for a good case and PSU, have yet to add in water loop and extras like fans, LED's, Cathodes, Front Panel stuff, etc) http://pcpartpicker.com/p/rTln
What are you going to power with it? 600W is enough unless you have/are going to add multiple graphics cards.
Well, it's the standard 3570k + 7970 build, but I like making my computers look good and cool decently, so I'm doing a custom water cooling loop, adding a bunch of front panel stuff, and I'll end up putting in some Cathode Tubes and LED fans and stuff.
[EDIT] Build link is in the OP, unfinished due to some customization stuff.
I think that overhead will be filled by the Cathodes and stuff.
If I need a better power supply because of the extras I will be adding, let me know.
I would go ahead and just get the 750 if you plan on adding a bunch of stuff in. I am not sure how much power Cathodes take up, so I couldn't tell you, but I can tell you when you add a bunch of stuff in it adds up fast.