Looking for the best matching gpu

Hello,

There are so many GPUs are there, so

it is really confusing when I need to make a choice.

My computer has

m3a78-t mobo

hd 4830 gpu

phenom ii x4 965 be cpu

4g ram


I like to play battlefield 3 1920x1080 with low or middle setting above

60fps. Right now, I am getting between 30~45 fps.

My question is what is the best gpu that my cpu can handle.

I don't think budget will be problem since my cpu isn't good enough to handle

those high quality gpu  

thx