Can u see/hear/feel the pump (not the fan) moving fluid, cause that might have failed
Make sure you don't go overboard on cores, and read the fine detail specs cause some CPUs run at low clock speeds when in full use and only boosts 1 or 2 cores to the package listed boost speed
Arma 3 only uses 4 individual cores so others will be used for other activities
Newer Gen do have improved instruction coding which will give better performance per clock speed from what you have but not by alot