Those game aren't all that CPU heavy, so you could probably get by with the i5 if you wanted to save some money, though the i7 would be a bit more futureproof if you want to run this system for a while before doing another CPU upgrade. If both setups are the same price, I'd still go i7, the 8600k can be overclocked but the 8700 already runs at 4.3GHz on all cores anyway with standard TurboBoost behaviour and higher clocks do not always compensate for lack of threads, as the performance of the older 4 core/4 thread i5s in newer games have shown.