Depends if you have agp or pci-e. For agp there is the Nvidia 6800xt, Ati x800 series (I like gto) and Nivida 7800gs (Most popular it seems). On pci-e, it seems best bang for your buck is 7900gt by evga (around 230 with rebate I think).
It seems Everest is not available for download anymore. Been like this for some weeks, maybe months now. Hmmm, wonder why. Try Sandra or cpu-z to find out your motherbaord and then look to see if it has agp or pci-e, or even both.
i3 540 @ 3066 MHZ
4GB DDR3 1600 1T 9-9-9-28
HD 5750 @ 850/2400
Antec Lanboy Air