If you only want to play bf3 you should just get it for console. Even though the graphics are *** compared to on PC. You are wasting money and time if you're willing to build a gaming PC JUST for one game.
so u want to play bf3 only? or mw2 and bo2 aswell? Whatever you decide to play still requires a decent pc. (unless its just cod that your playing) So how much are you willing to spend?
( in dollars $$ )