Noob Need Help on gaming GPU

I am building my first computer and no very little about computer hardware however I am very eager to learn. I want to maximize my framerate for my new computer but I am unsure which gpu or gpu's using crossfire I should get. I am willing to drop around 500 max on a gpu. If i used crossfire are there any new games that would not support this? as well how would getting two 6950 2gb overclock look. I might just purchase one then purchase the next later. What can I do to really maximize my graphics. Again I know practically nothing. I will be playing mainly rpgs skyrim and star wars the old republic. How should i spen my 500 dollars. Any help is greatly appreciated.