Change that PSU to an antec, corsair, cooler master, or rosewill (stick to their single rail models)
Really, OCZ is a good brand and all, but the whole 'Xtreme' were not good power supplies. The 500w rating is not where it's rails max necessarily, but where the voltage ripple passes outside of allowed ATX spec. Anywhere past 400w being drawn from that rhing will be highly unstable and shorten the life of your components.
<ninja edit>