I'm not a nerd in pc's, i dont really know that much about whats inside a pc and all that stuff. But I'm thinking of buying a gaming pc for around 900 bucks that will play counter strike source, team fortress 2, left 4 dead 2 and other games on a good level. I was thinking of buying this one off ebay for $750,

http://www.ebay.com.au/itm/INTEL-CORE-i7-2600-QUAD-GAMING-DESKTOP-SYSTEM-COMPUTER-PC-8GB-DDR3-RAM-1TB-HDD-/150682241885?pt=AU_comp_dekstop&hash=item23155c8b5 d

or

http://www.ebay.com.au/itm/INTEL-Core-i7-2600-Gaming-Computer-8GB-1TB-GT210-1GB-HDMI-Quad-Desktop-PC-/230668762744?pt=AU_comp_dekstop&hash=item35b4edfe7 8

Sorry i don't know much about PC's and if you have any good finds on eBay.com.au can you please paste them into your comment