Well I don't know how taxing BF4 will be, you could go with: i7 4770k ($330), 7970Ghz ($375), and (for example) ASUS MAXIMUS VI HERO ($200)
If you wanted to save money you could swap to i5 4670k ($240) and/or go with a cheaper mobo (probably down to no less than $100)
Other graphics options would be GTX 770 ($400), GTX 780 ($650), 7970 ($300)
My philosophy is, you don't necessarily need to spend your whole budget just because you have it, so if you wanted you could save~200 for a future upgrade
Edit: I just noticed you said 100fps on med settings (I really need to pay better attention). So if you are looking for high framerate with reduced visuals, then i5 4670k (or even i5 4430($190)) and a 760/gtx 760($250) with a $100 mobo would probably do you fine
All of this is just my opinion, it would probably be a good idea to look at charts/benchmarks before making a final decision.
Best of luck!
-Connor