As far as Nvidia goes a GTX 770 2GB or 4GB will get the job done. I am no really familiar with the AMD side of things but whatever is equivalent I would imagine will work for you! An AMD 280X looks like it will kick some ass.
If u want to play on ultra @1080p then u need GTX770 or R9 280x. 280x is not mentioned in this benchmark but it is similar to 770 at $300. 780 and above dont have a good price to performance ratio. 780 will cost u more than twice as much as a R9 280x and it will only give u 17% improvement.
You guys really think so? I mean, from what I've herd, a 770 is terribly overpriced ($400). But, I am open to all options and should have an adequate amount of money to buy a GPU by the end of this year.
What is the resolution you want to play BF4 with? If you're not going over 1080p or intend to do 3D, there's no need to go any further than a 7970(standard or Ghz edition). BF4 will be one of the first games to feature Mantle API support, which could potentially be a big performance boost for Mantle compatible cards such as the 7970.
Mantle is an open platform so Nvidia can jump in later down the road as well, but as of right now there has been no word from Nvidia regarding Mantle. BF4 will be getting Mantle support this December.