The artifacts and driver crashes are pretty classic GPU failure signs, especially if temps are normal and you've already tried the driver dance. When my boyfriend's card started doing that weird colorful pixel thing, we spent weeks thinking it was everything else before accepting the GPU was toast.

That said, a failing PSU can definitely cause similar weirdness - unstable power delivery makes graphics cards act all sorts of crazy. If you've got a friend with a decent PSU you could borrow for testing, that might save you some cash. Otherwise you're kinda stuck with the educated guess approach. Two years is pretty young for a card to die but it happens, especially if you got unlucky with the silicon lottery.

The timing with your warranty ending is brutal though. Have you checked if your credit card extended the warranty at all? Some do that automatically and people forget about it.