We know that gaming is a stressful thing for computers, especially the video card. It's possible you don't have adequate cooling and heat is causing you problems. Can you monitor the GPU and CPU core temperatures while idle and then while gaming to see if they are reaching 70 C or higher?
Another possibility is the PSU not being able to supply enough current as the video card tries it's best to deliver the frames to your monitor. I would think a Corsair 650 W PSU would work with your components. Are you using two PCIe power connectors to the video card (assuming it has two 8-pin plugs)?
Are you overclocking any components? If so, I would return to nominal settings.
I would also look for an updated BIOS for the motherboard. If you aren't running on the latest version, I would highly recommend you flash the BIOS and then see if that addresses your problems.
As Albert Einstein said, "I could have done so much more with a Big Al's Computer!".
