The goal is to hit at least 50fps. Closer to 60 is best cuz at that point you are reaching the limitation of the monitor. Also, benchmarks are an approximation and give you an idea of what to expect. According to the above chart my 280x should get averaging 54 fps on Ultra. I have run FRAPS and have found the average to be more like 60fps with some dips into low 50s. This is with 4 x MSAA on.
I had a 660ti which is almost the same as 270x, but 270x probably slightly higher. I ran BF4 on High getting 60fps. Then I went to Ultra and had to turn off MSAA to get 50+fps. It was definitely playable at that level.
If I didn't own a GPU and wanted one for BF4 then I'd buy either a 770 or 280x. This is assuming I can afford it. Depending on...