BEST CPU for playing Arma 2 and later Arma 3 on?

So I LOVE the Arma series and Arma 2 currently will not allow me to crank up my view distance over 3000 with my Phenom II x4 (this is on Arma 2's main map, Chernerus) and I wanted to upgrade my CPU around Christmas time. Since I want to be able to play Arma 2 with 10,000 view distance (those of you who have played it know that this is difficult) and achieve stable frame rates (my GPU will have no problem, Arma 2 is 80+% dependent on CPU power) so I figured Intel would be the way to go, and therefore I will need to upgrade my mobo as well.

I currently have, in my computer, a Phenom II x4 965 BE with an HD 7770 for my GPU and so far they have served me well, but not in Arma 2. So, since I ALSO plan on Crossfiring my 7770 at Christmas time I will need an Intel motherboard capable of Crossfire and also of supporting either an i5 or i7 type CPU.

I do not want to spend OVER 400 dollars on an Intel CPU but below that, I think I can manage, and I was REALLY thinking about getting an i7 of some form since I hear those are great. I also hear that i5's are fantastic, but the problem is that Arma 3 is said to be IMMENSELY difficult to max out and Arma 3 is scheduled to be released later this year. If there is, however, an i5 that could possibly run Arma 3 with VERY high view distance, then I would love to hear about it and I will also have you know I am MORE than fine with overclocking my equipment, but I might need suggestions on a CPU cooler if that's the case. Anyways, since I am most likely going to buy an i7 processor, which is the best one out there for under $400? Also, I need a motherboard that can support it AS WELL AS crossfire (you know, AMD GPU's) and I don't want to spend more than 100 dollars on a motherboard (I'm cheap).

Thank you for your help in advance.