Have to isolate the problem one by one. I suggest you test the CPU first with programs like OCCT or Prime95 as it can test the RAM at the same time. If everything look stable, then it could be either the display adapter or driver issue. PSU is usually the last thing you should consider unstable.

Have you check your GPU temperature? Furmark generates lots of heat and can be the source of problem.

Btw, 5 min of Prime95 is way too short to test a CPU.

Run a 3D demo like Unigine Heaven and check the temperature with HWMonitor.

Prime95 requires at least 8 hours. OCCT is more sensitive but need at least 1 hour. But anyway, your problem doesn't look like a CPU problem.