My PSU is the OCZ GameXStream 700W:http://www.ocztechnology.com/products/power_management/ocz_gamexstream_power_supply-nvidia_sli_ready_
Well, I opened up my game again, i I'm getting now 50-80FPS, so I think is normal now, and I know this is kind of stupid but I did not change anything, the only thing that I turned off was the HBAO, and my FPS went up like 10FPS, but still, If I turn it on, I get like 40FPS, so I don't really know what happened the first times that I opened up the game (I was getting 20FPS), but now it is working like a charm.
I love my new Graphics card, is just amazing, it gives me a lot of FPS with every game.
Thanks for all your replies.
PS: I really did not change anything special, I was only playing with settings, putting them on low, high and testing with anti-aliasing and that kind of stuff, at the end, I'm getting good FPS now, I do have the latest drivers though.