Alright so the issue im having is that my computer starts up and works fine, that is until i play video games at which point my computer restarts randomly. In addition when i have tried to connect more than 1 graphics card the graphics cards wont start up. I am assuming this is a faulty power supply issue more than anything and that my computer shuts down as the graphics card puts more stress on the power supply, additionally that my power supply cannot run two cards now which is why when two are connected they dont start up.
My power supply is a thermaltake 1200 TRX which ran my two gtx 680's fine in the past.
You could try loading up the system by running Prime95 and Furmark and seeing if the power draw causes the issue. However...if the PSU is supected faulty, the safest thing to do is replace it. I've had a PSU take out my motherboard before, and it was a good PSU, not a generic unit.