100$ would be FAR better served by sticking that money into a GPU, the performance gains in any game out there going from say a 960 to a 970, around 100$ difference depending on the brand/etc, are very measurable, where as that 100$ difference in CPU, which is almost exactly the cost difference between the i3-6300 and 6600k, if using the same video card/ram/mb/etc, isn't nearly as much. Plus if you're going to get a "k" model, you need a better cooling system in order to overclock it, which is the entire point of an unlocked CPU, as the K and non -K models perform virtually identically when clocked at the same speed. Such a cooler is another 40$ minimum for say the Evo212, which is the cheapest option by far, and a really good cooler that allows true o/c potential is going to be another 100$ easily.
I'm not sure how that AMD cpu in the OP build would perform vs an Intel "K" cpu of some type in the 100$ more costly range, not exactly, but I'm reasonably certain it won't make nearly as much difference in performance as a 100$ better video card.
I do agree though that an Intel K cpu is the way to go, so long as cost isn't a concern, but if it is and you're going to stretch for something, and obviously the OP is a budget build, if he put 100$ into a faster GPU, like a 980 on sale+rebate which can often be found for around 110 or 120$ more than a 970, it would give far greater gains in all games than going to a 100$ more costly CPU, AH3 included as the OP said this is the major game that'll be played.
