It would be worth testing more of your hardware - it can be very difficult to pin down which hardware is causing problems as so much of it interacts. Memtest86 is the recognised test for memory, I advise running 2 tests back to back with 4 passes in each test for a total of eight passes. Furmark is the recognised test for the GPU and Prime95 for the CPU.
Hopefully one of these will help identify any hardware issues.