Pull the board back out of the case and see if it fires up sitting on the anti-static bag that it came in. Don't connect anything except the PSU leads. Briefly connect the power on pins on the motherboard and see if it gives the "no memory" code, typically just long beeps. Turn the PSU back off, add the RAM. Power up the PSU, do the pin connect thing, and see if you get a single POST beep.