fluffybacon said:
Get a 4870? There 100$(ish) right now and will max out everything in existence, and probably continue to do so for a year or more.
Or a 5770/5870/5890 if you want dx11, I guess.
Also, there is no such thing as rendering cards, It's the same hardware with different drivers.
Same GPU, not quite the same hardware. Workstation cards do have some hardware-level optimizations. But your point is taken. One big difference between rendering cards and gaming cards is the driver, with video memory being of secondary concern. As I've been discovering these past few minutes, it
is possible to softmod (ATI cards at least. I'm guessing it can be done with Nvidia GPUs, but I haven't checked.) to act like a FirePro card, which makes a huge difference in rendering performance. Based on that, and given the OP's budget, I would go with something like a Radeon 4870, or any high end gaming card that has successfully been softmodded to run like its professional brethren.
Basically, if you go that route, you're using a ~$2-300 card to do the work of one that costs about five times that amount.
Edit: And by the way, here's an example of how big a difference there is between a workstation card and a gaming card:
http://icrontic.com/articles/perspective-the-radeon-hd-5870-vs-the-firepro-v8750