Technology, video, phone & computer questions

[Angrboda]

The only real big question remaining is whether replacing the video card has resulted in a stable system; the hard resets were intermittent, so I have no way of reproducing conditions which would be expected to cause a reset.

Could it have possibly been overheating of GPU/CPU?

No. This motherboard has always been problematic. I RMA'd it in the first year, but Gigabyte has a policy that, if it passes the tests administered by their test machine, they just send the board back to you. So it's a bad motherboard, but it's problems generally can be minimized to the point that it's usable.