[PsYcNeT]

On second thought, if the +12v Rail(s) is blown on your PSU it would cause the system to not boot; did your test card have any PCI-E 6/8-pin connectors at all? If not, it could be what DIF mentions above, it could be the +12v rail(s), or i could just be the card itself is faulty.

Did you not get any error beeps? Often if the GPU isn't sufficiently powered it will beep when POST fails (this typically happens when the PCI-E connectors aren't plugged in at all).

No beeps doesn't mean it's not the card, but it might be.

Honestly, this type of situation is where you can kind of take advantage of MemEx's return policy. It's a ####ty thing to do, but you can buy and wire up a new PSU and see if that resolves the issue. If it doesn't, you can bring it back and return it for credit, and put that towards a GPU purchase.

EDIT: Just saw you are in Portland, this may not be an option :/