Repost (issue not solved) mutiple gpu's, multiple builds all CTD

First off, long time viewer, rare poster... the help these forums provide has meant i rarely have to post a question, and most if not all theads are answered by people more tech savvy than me... anyway, i digress....

this one has me completely stumped, I will start from the beginning, bare with me as i want to give out as much information as possible

first off I purchased all the gear for my dream x79 build

ASUS Rapage Formula (x79)
ares 32 gb ram kit (quad channel) (1600)
intel 3930K 6 core
agility 3 ssd
storage drive
evga gtx680
silverstone strider 850w
water cooling loop

well thats the basic first build

so i put all this together, crank it up, temps ok, benchmarks ok, all is well, over the moon.... then i go to play a game.. crash to desktop...over and over again across all games. I then returned the gtx680 and swapped for a gainward gtx680 phantom, hoping this was a a dogy card issue i threw it in and.....same thing.

I finally got a fix i was not happy about at all, witch was to downclock the gpu significantly, along with leaving the cpu standard speed. this was fine but started noticing it crashing to desktop but only after a much greater time.. by this stage i was fed up and after much forum browsing and trying EVERYTHING i thought 'stuff it' I will get a 7970 instead (got 2, actually) well this time, after the same amount of time, it did not crash to desktop but hung..you know, that horrible hang where the audio hangs as well....

DAMIT! i said.. wth is going on...power supply perhaps? so i replaced with a corsair ax850.. SAME PROBLEM. replaced memory with corsair dominator gt quad channel...SAME PROBLEM.

by this stage i was getting seriously depressed and dipping into money reserved for other things (the missus was not happy) but made the big choice of doing a new build on the z77 platform incase it was a mobo/cpu issue (bottlenecking or something). so along came the second build

z77 sabertooth
intel 3730k
intel 520 ssd
asus zonar audio card
new storage drive
new cooler
using the brand new quad channel dominator ram in it... should still work if i have my facts right
using the ax850 psu I purchased as a possible fix on the old build
and trying either the gtx680 (the second one i got after replacing the 1st in the hope it was a gpu issue)
and the 7970


all went together, and with the loony bin on standby I fired up bf3 and skyrim...................... SAME BLOODY THING, both 7970 and 680 presenting the same issues

at this point, as you can imagine, i was damn near ready to cry, i mean how can an entirely new build using either gfx card (confirmed working in friends builds) present the same issues!!!!

so this brings me here, with many thousands spent, 2 of the most modern 'all out' pc builds sitting here, with the option of a 680 or a 7970 in either of them... i should be loving it, but im not

I am at a loss and about ready to go and buy an xbox

edit- i have tried all manor of connectors, cables, dvi-d hdmi...etc etc to connect to my 2560x1440 monitor.. makes no difference, my last and final idea is the power from the wall is dodgey.. spikes? drops? could this do it? and would a psu not handle that flux and deliver stable power to the rails anyway? (no other devices connected present with issues)

i appreciate all of the help I have gained from you guys in the past and would love some thoughts on what direction to take

warm regards
slade