Is the new PSU branded or just another trashy one? most cheap PSUs tend to be a major cause of problems. Also, you have given no time frame at all since all this happened, it could be a driver problem for the GPU. If everything fails I think it may be either the processor or the motherboard (I've never heard that a processor can cause a PC to crash unless it is an overheating problem, otherwise the PC wouldn't run at all.)
Things to try and look at:
1) Try monitoring the temperature of the PC components until it crashes using CPUID.
2) Try using the processor on another motherboard and see if the crashing happen to the other PC as well.
3) If the problem happened after a driver or a BIOS update, you should look into downgrading to the previous stable one.