I would head up for a 110 dollar 9800GT, a 50 dollar 650 watt power supply, and perhaps 70 dollars or so worth of RAM that is compatible with your mother board.
I personally blew way too much money on my PC, experimenting with a BFG GTX 280 (Don't get it... they may have all year customer support but it's one of the shittiest I have ever encountered) and am currently waiting for dual HD 4870's.
But, what was mentioned above is all you really need, when I first upgraded my computer, EVER, those are the three components I changed out, and managed to get a good average of 60 FPS on Counter Strike Source with all settings maxed, 1440x900 resolution. Got a bit hot though, getting a 120 mm fan may also be a good idea.
I personally blew way too much money on my PC, experimenting with a BFG GTX 280 (Don't get it... they may have all year customer support but it's one of the shittiest I have ever encountered) and am currently waiting for dual HD 4870's.
But, what was mentioned above is all you really need, when I first upgraded my computer, EVER, those are the three components I changed out, and managed to get a good average of 60 FPS on Counter Strike Source with all settings maxed, 1440x900 resolution. Got a bit hot though, getting a 120 mm fan may also be a good idea.