Help upgrading GPU

Planning on playing games such as BF3, Crysis 3, League (yea I know my toaster can max that) and so on. I am looking to get a GPU that at the very least can get > 40 FPS in those games. I am looking at the 7970 or the 670 but really have no Idea which one to grab or what brand. Assuming price is no problem which would you guys recommend? Plan on playing on a single monitor btw at 1080.

Intel i5-3570k
8GB RAM
Gigabyte GA-Z77X-D3H

Thanks in advance for the help!