As long as your power supply can provide enough juice (and you don't have some low profile case) you can put pretty much whatever video card you want in there, and it becomes a matter of how much money you want to spend. But before we get to that, whats the wattage and make of your PSU?
ugh, dont even consider that thermaltake. get the corsair. 650ti is a nice gpu that can be had for 139$ on sale
What's wrong with the Thermaltake? There is no reason why it wouldn't be just as good as the Corsair model, especially when you consider that they both have the exact same OEM, Channel Well. One simply has a Corsair sticker on it and the other has a Thermaltake sticker.