it probably will, an athlon II x4 645 is an odd choice for gaming, same price as an fx 4100 so most people take that.
I can tell for sure it will bottleneck Arma 3 because Arma 3 is very bad optimized and eat´s most CPU´s.
i would go for an fx 4100/4300, unless your mobo isn´t supporting that ofcourse