STOP 0xA IRQL errors are usually defective RAM modules, but can also be caused by corrupted drivers. The error basically means that the OS or a driver attempted to read something that was loaded into the system memory (i.e. RAM) and the request was denied (either because the segment of RAM is broken/inaccessible or a driver requested data that wasn't there).
It is really up to you if you want a new PC or not. Your CPU has a few years in it yet, your graphics card produces heat like a toaster (but then the GTX 480 cards always did) but it will keep you going for a while yet if you give it a decent clean. A RAM stick (or slot) is likely kaputt, and diagnosing memory is a pain in the backside because there are so many variables to test (1 stick in each slot, then a different stick in each slot, then both sticks in two slots, then both sticks in other slots etc).
Giving the graphics card a good clean with some canned air (3-5 euros at Saturn) would likely reduce the noise and temperature significantly if you haven't done so in a while.