yxd0018 :
Pretty much eliminate the PSU. All voltages are fine and swapped with a working PSU still the same symptom. However I can clip jump start the PSU while it's plugging into MO. Thought it's switch issue, but swapping with reset cable yields the same result. That only leaves MO issue. Am I right?
Your PSU is of great quality, and has lots of protections which should protect it from causing problems, I remember my old computer got killed (Motherboard and CPU both died) because of a power outage, but in that case it was the network cable that caused the issue (Probably the router got high voltages because of a lightning struck or something, and the voltage was then passed to the cable..)
Anyway, when you press start button, any cooler (From PSU/CPU) starts spinning? Also, does the hard drives spin too? For me it sounds like a motherboard issue but the cause of it can be other things.