Just brew it: Thanks for the reply. No, I'm absolutely certain it wasn't the 6-pin connector. I used the 4+4 connector. Split it in half, plugged it in. Since it's keyed, there's no way I could have plugged it incorrectly.
OK, that leaves us with defective PSU, or motherboard was already dead (CPU voltage regulators fried), and the new PSU merely put the nail in the coffin.
Besides, there's the clip that clicks in place once it's plugged in.
PCIe connectors have a clip too. (But that's beside the point now...)
Now my dilemma is, if it's the PSU at fault, I could return it and argue that my components were fried because of it. If the PSU checks out fine, I'm certain the store won't even take the PSU back, leaving me with $80 down the drain and several components dead. I don't have a voltmeter and neither do I know how to use one so I can't really check.
Know anyone you can borrow a voltmeter from? (We can walk you through using it.)
Got a motherboard and CPU you don't care about that you can use as a guinea pig?
I guess worst case try to take the PSU back, and if it tests out OK then that's pretty good evidence that it *wasn't* the PSU's fault.