can it run bf3 on ultra smoothly ?
That depends on your definition of smoothly. 30 fps, maybe. I would check this site for a benchmark of the 660. Actually Ill take a quick look.
Mind you that is with a 6 core i7 overclocked to 4.2GHz. So your i3 will deliver less fps. SO on ultra i doubt it runs at 30+, maybe high or med.