Noted your comments on the PSU and on the CPU fan.
Until troubleshooting is finished and you are up and running OK, it is advisable to have the whole rig running at Defaults setting.
First, turn off the TPU switch (Disable)
The CMOS actually stores the setting which have been configured in the BIOS. When you switch off the computer those setting in the BIOS are lost, but the CMOS has it's own battery so the BIOS settings are saved. Now, I hope I have this bit right. When you switch on the computer the BIOS checks the CMOS, runs a check sum, (if wrong, no Boot) if OK, settings are configured again in the BIOS and POST is performed. If the BIOS is updated,/flashed, and the CMOS is not cleared, it can set some wrong settings in the BIOS leading to instability. If you make changes in the BIOS, when you save the configuration, the new settings are stored in the CMOS ready to write back the next time you Boot the computer, if the configuration are wrong, no boot, you would need to clear the CMOS. Clearing the CMOS memory sets all the CMOS memory locations to FFH this is detected by the BIOS which then loads its default values.
Second.Please follow the instruction on Page #20 of the MB user manual, (Clear RTC RAM (3-pin CLRTC)
Important. You will need to enter the BIOS and reset the time/date and language. The RAM timing will be set to defaults. If you have higher speed RAM installed, do not change it until the system is stable. Just go to the exit menu, save changes and exit.
Third. Whatever the software you are using for the GPU, see if you can revert to Default setting.
Fourth. No crashes with furmark, crashes with games. Check to see if any of the games load overclock setting.
The LEDS blinking on and then going off is the correct behaviour. The Boot Device Led staying on after the computer crashes does indicate a hardware device is faulty or possible a driver issue.
If installing a new GPU does not solve the issues, we need to look elsewhere.