The LGA 775 socket is EOL so you would be better building based on an AM3 (budget minded) or LGA 1156/1366 (higher up). These will provide better overall performance than your build.
If this is a current running system, only recommendation would be to look to upgrade your video card to a newer ATI or Nvidia Fermi card.
Well its not a system that i have someone offered to sell it to me they had it for 5 months and is selling it because of travel... their asking price is 450US dollars
if not what gaming system would be you vouch for note i have been reading up but i like to hear from gamers that have been their build that... knows how it runs...