yup, pwede ang 500W... even 450W kaya na sya but less head room... pero, if you're planning for SLI or Xfirex for GTX 660 Ti or HD 7950, mas swak gyud ang 750W to 800W... below is a review ana na PSU...
FSP Everest 80Plus 800W PSU - Introduction
then, review from the users from New Egg... for reference lang...
Newegg.com - FSP Group Everest 800 800W ATX12V V2.2/EPS V2.91 SLI Ready CrossFire Ready Modular Active PFC Power Supply