Robert covered what needs to be done, that reduction of the system is the best to help pin-point possible bad component to include mtrbd. or psu. Even though you have a decent psu, a voltage rail could have blown. Cooling is important if that was a contributing factor in the system failure, do review that once the system is up and running. Excessive heat will stress componets and psu. The psu loses output stability and the componets get flaky. I tend to lean towards a bad psu, but again anything can be iffy. If you have access to a 2nd system, use that as a test bed.