according to that website the best card that you would be able to afford would be around a 7750 its around 6000....the only problems is that the card is really underpowered for your system. Your system would benefit alot from a much better card
hmmm...I am considering ATI Radeon HD 6670, 5570, 4670, 5670, Sapphire ATI Radeon HD 2600XT.
Also tell is whether to take DDr5 or DDr3. Which one is better?