I wouldnt normally suggest this, but since you seem to have tried so much, its probably worth a try. Getting the correct up to date drivers is not always as straight forward as it seem. Try using driverbooster (http://www.majorgeeks.com/files/details/driver_booster_beta.html)and letting it update all drivers except gpu is if tries (uninstall driverbooster after and ignore the bogus 1 driver ad! There maybe other programs out there like this, but I have found this the easiest and works pretty quick and fairly well, at least for myself and did help me sort some of my own issues).
Failing anything else, you may have to go back to basics:
Remove all unneeded hardware and reset the cmos (normally jumper on mb or remove battery for a few mins):
Remove all hdd/ssd apart from main drive
Remove all usb devices (maybe even try different kb/mouse)
Deffo take the sound card out and 1 of the gpus
Check all power cables
Even though your temps are just fine, it probably worth checking the cooler is securely on but not too tight (this has been known to cause problems if too tight, but its rare)
Only use 2 ram sticks at run at 1333
Test for as long as you are happy, then add each thing back in slowly and test after each. Its a pain but needs must!
Failing anything else, you may have to go back to basics:
Remove all unneeded hardware and reset the cmos (normally jumper on mb or remove battery for a few mins):
Remove all hdd/ssd apart from main drive
Remove all usb devices (maybe even try different kb/mouse)
Deffo take the sound card out and 1 of the gpus
Check all power cables
Even though your temps are just fine, it probably worth checking the cooler is securely on but not too tight (this has been known to cause problems if too tight, but its rare)
Only use 2 ram sticks at run at 1333
Test for as long as you are happy, then add each thing back in slowly and test after each. Its a pain but needs must!