|Starting the system with the CMOS jumper in the clear position can damage the motherboard. |
Now you need to evaluate exactly where you are. I am not sure if a bad motherboard can ruin a new power supply. I suppose it is possible if there were some sort of short in the board. That said, most of the time there is a power surge when a power supply go out and that can fry components on the board. Once that happens I don't think there is continuity anymore.
Bench testing a motherboard takes many components out of the loop so it is a good idea.
I suggest you try the new PSU with the new MB & CPU outside the case. Only things required are as follows:
MB with CPU/HS/fan, 1 stick of RAM, power supply connected to board including auxillary 12V connector, video (on board or add in), monitor and keyboard.
No case wiring, drives, external hardware other than mentioned. If the board POSTs then install back into the case. Start the board by momentarily shorting out the two pins that the power switch connect to.
Be sure you have properly applied thermal compound and you have the CPU fan connected to the header marked CPU fan. Double check the CMOS jumper is in the run position.