genca :
And as everyone said, try to get K version and buy z370 motherboard. Currently, you wont really see difference between 8700k and 8700 but for a few years you will see.
I didn't say that. : P
In a few years, if there's any difference, you'll only see it when overclocking. At stock clocks, the 8700K and 8700 will be nearly identical in performance. Just look at the CPU tests in Tom's Hardware's own review, for example...
https://www.tomshardware.com/reviews/intel-core-i7-8700-cpu-review,5638-8.html
Even when pushing these CPUs to their limits, the differences in performance at stock are almost nonexistent with an identical cooler. Lightly-threaded CPU tests showed up to a 3% difference at most, and heavily-threaded workloads saw no difference whatsoever, since both CPUs have the exact same boost clocks when all cores are active. This minimal to nonexistent difference in performance carried over to their gaming tests as well.
The differences in CPU-limited workloads were more notable with their 8700K overclocked to 4.9GHz, amounting to about 7-10% more single-threaded performance up to around 15-20% more heavily-threaded performance over the 8700. For gaming, the differences tended to be smaller though, even with a GTX 1080 running at 1080p. And again, an overclock like that requires not only a more expensive processor, but also a more expensive cooler at the very least.
As for the 212 Evo, it certainly wouldn't cut it for overclocking an 8700K, but it's also certainly better than the inadequate Intel stock cooler that the 8700 ships with. It might depend on case airflow and room temperature, but I suspect it may be enough to enable an 8700 or 8700K to maintain it's stock boost clocks under real-world workloads. A stress-test like Prime95 might result in the CPU dropping to lower clocks, but that's not exactly a real-world workload, so performance there shouldn't really matter much. At the very least, it would likely be worth trying the 212 Evo and seeing how it performs in a somewhat more realistic heavily-threaded workload like Cinebench. Of course, I'm sure it would be more audible under such a workload compared to most higher-end coolers.
One other thing to consider when deciding on whether to get a Z370 motherboard is if you are willing to pay a little more for faster DDR4 memory. While it makes a bit less of a performance difference on Intel's CPUs compared to AMD's, moving from DDR4-2400/2666 up to 3000/3200 can actually make a 5% or greater performance difference in many workloads, including gaming in situations where performance is limited by the CPU, rather than the graphics card. That can actually make for a larger difference in performance than you'll see when moving from an 8700 to an 8700K at stock clocks. And at least at online retailers in the US, DDR4-3000 only costs around $10-20 more for 16GB than DDR4-2400/2666, so faster memory is something you may want to go with if you decide to get a Z370 motherboard. Intel's other motherboard chipsets don't support speeds over 2666. These faster RAM speeds are technically considered "overclocking", but the RAM is rated by its manufacturer to run at these speeds, and enabling higher memory clocks typically amounts to simply selecting its XMP profile in the bios, and unlike CPU overclocking, shouldn't require a higher-end cooler or increased fan noise.
I don't think it was ever mentioned what the rest of this gaming system or its overall budget was going to be though. What are the planned system specs, and what resolution and refresh rate will you be gaming at? If you were intending on pairing the processor with a more mid-range graphics card, then it's very possible that putting the money toward a higher-end card would be a lot more beneficial to performance than components like the CPU and RAM.