I've fried my G. Skill PC6400 overvolting before. Everything worked fine, overvolted it and killed it. I had to isolate the bad DIMM and RMA it. Not sure about the PSU being bad.
That gskill is suppose to run at 2.1, at least the 2 gig sticks I was playing with did. So I doubt you overvolted it.
First off, I'd reset CMOS, there is a button on the exterior of case for this purpose. Then try to boot with one stick. If you can do that then go back into BIOS and set it to 2.1.
If that fails then try another brand of RAM if you can. Maybe the Maximus just doesn't like what you have, though it is working OK on my friend's machine.
Try another PSU. You have a great unit there but it could be a lemon, happens to the best sometimes.
If that fails take the PC apart and rebuild it barebones outside of the case. No drives, just cpu/fan. 1 stick RAM, power, video card, monitor.