If you want the maximum performance in ArmA 3 go with a K CPU from Intel (AMD CPU's perform very bad in ArmA 3, i'm talking from experience). If you can get an 4790k or 6700k and OC them to 4.7 GHz that would give you an amazing FPS boost in A3 multiplayer, depending on what mod you are playing. Also I recommend going for a skylake build and use DDR4 memory because high frequency memory has been proven to boost the fps by 5-10 or more in ArmA 3