Ultra psu’s are not known as particularly great ones, but one use is a bit much even for them. There are such things as power supply testers, like this one: http://www.frozencpu.com/psu-165.html?id=s7uYuWwT, but you might check a few other things first.
Loose connections are the first thing to look for. You’ve probably already thought of that. Examine the power connector on the motherboard and see if there are any scorch marks on the either the cable or motherboard connector. You have the P4 (square 4 pin connector) hooked up as well? And the cpu fan connected?
You can bypass the power switch by making temporary contact across the two pins that the power switch line hooks up to on the motherboard (but if there are no leds lit on the motherboard at all, I suspect this won’t work).
The only other thing that comes to mind is to try another psu in the computer. By the way, 650w is overkill for the components you’ve listed. A good 400-450w psu from a reputable company would be more than sufficient. Look at Corsair, Seasonic, Fortron Source, PC Power and Cooling, Enermax, among a few others, for good psu’s.