Compuyer randomly shuts down restarts

Hi... My new build was running fine but since about a week ago i started getting this strange and serious problem with my computer.... I investigated myself through testing and researching but i have no idea what is causing this and how to fix this....

so the problem is that my computer just randomly shuts down without any warning and powers back up.... The shutting off process is like when u unplug the power plug from the wall so no window shutting down process and then powers back up and works fine again.... I tried to rule out when the restarts mostly when im playing games AND browsing web... I run duel monitor on one screen i play wow and the other screen browse web and thats mostly when restarts happens.... And if u see my system its way over kill for wow.. Hell i can open like 3 or 4 wow clients and still get a good fps.. Cpu usuage is at maxx 60% and i tried with default setting with no luck.... When i stress test with aida 64 it DOES NOT restart even when i do it for well over an hour....but when i try bench marking with 3Dmark11 the computer always restarts and actually never completed the bench marking due to that......

I have a PSU voltage meter from thermaltake and it is fines all the voltage displayed on meter is +/- maybe 0.1 or .2 at max with 700w im sure its enough to power GTX 680 and i5 3570k on stock setting..... I also formatted my computer just yesterday to rule out virus and i did hard format with fresh window install....

Also tested my RAM with memtest for around 7-8 hrs and had 7passes with 0error.....

As u can see im starting to get reallu fraustrated and frequent restart will lead to hardware damage at some point so id really like to fix this problem....

Another thing i read over the internet is if i disable Vdroop or LLC i might fix this problem but i dont see how they are related and my Asrock extreme 4 z77 board does not have an option to diasble that feature only has auto and level 1,2,3,4

and yes i did change the setting in window 7 that autometically restards when getting error and unticked the box....
Lastly its not god damn temperature as i did stress test with aida 64 while monitoring with hardware monitor..... Although gpu did raise up to around 74 and cpu rarely 50

Even the voltage meter read psu fine can the PSU still be the problem? its really not a amazing PSU ita from ocz modularstream X or something...
Im running out of options... Please can anyone help me solve this problem?? any tech experts out there?