Are you taking recommendations on psu/case/hard drive/etc as well or are you gutting a previous build? What resolution are you intending to game at?
BF3 is very CPU intensive and on ultra you will be much better off with a 2500k. The 2120 can handle it, but it isn't perfect.
I'm not a radeon fan right now primarily because of price/performance. The 560 ti offers 90% of the 7850's performance for 80% of the price. The 7950 and 7970 are better price/performance options and will get you better gaming quality, but are considerably more expensive.
I'm hearing $350 for the 660 ti most recently. Also why not go with 8gb of ddr3-1600 (low profile for the heatsink you suggested) for a few bucks more? http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Also if you're going to buy aftermarket cooling you might as well go all the way to the noctua nh-d14. It's significantly better performing, with load temps often 10 degrees C cooler, and it provides a long-term multi-generational investment (usually).