"Don't look at watts as much as amps. Personally, I run an evga 600 bronze. It has a single 12 volt rail with 49 amps. Pick something from a trusted babe such as evga, Corsair, antec, etc. Personally I like psu's with a single rail, but multi rail designs aren't necessarily bad either.
How big of a unit you need depends on how much you are running, but keep in mind watts don't always tell the story. I have about psu that is a spare that is 650 watts, but only has 38 amps on the 12 volt rail. So gives you an idea the differences between brands at times."
In the OEM's specs table, the +12V reads 45.8A.
"If GPU is removed, disconnect all drives, both SATA connections and power inputs to same...; disconnect USB headers to front panel, in case one is shorted... If unit is still literlaly powering itself off, try a known good PSU.... If still bad, your MB is bad, barring a 1 in 1,000 chance of aan actual CPU failure. Double check CPU fan plugged into right header..."
I removed the GPU, and disconnected all SATA so that only the 8pin and 24pin CPU and MOBO connections were in the PSU. I checked the CPU Fan connection and made sure it was in the correct place and tightened.
...and it still has the issue of turning off at the splashscreen.
I will go ahead and buy a EVGA PSU with more wattage, also putting the amps per rail into account as ohiou_grad_2006 had suggested. My previous pc I built used a 850W EVGA PSU so I might get something similar. I will let everyone know how I make out.