If you have to drive a long ways you can never go wrong by getting a PSU tester while you're there. I have one from Antec on the bench for a quick test... just good or bad lights, super easy and accurate. I also have one that tells me all the voltages so I can tell of just one line is low on power. They should be able to test the PSU at the store while you wait, it only takes a minute.
Ron