Upgrading video card.?

I have a dell Optipllex GX280 SD and i want to upgrade to a new video card. Can anyone help find one that suits my computer. I have a 210 psu|||anything from Nvidia, i have one and it works fine, but put a good GPU in a place with good ventilation, otherwise they overheat easily if they aren't fan or watercooled, i would say something like an Nvdia 9800GTX or for a good one but thats not over $500 something line an Nvidia GTX280