PSU doesn't make any difference in games, a branded 500W will handle that system perfectly fine.

Phantom, a review on Overclockers said about Corsair RAM being incompatible and a review on the P5QE (I'll dig it out later) said how the system wouldn't post with the Corsair RAM, so they used a different brand to get it to post, then updated the BIOS and then switched back to benchmark.