kardam.milushev :
Hey I,m gona be building a new pc mostly for streaming and i cant chose between Amd ryzen 5 2600x with x470 Aorus ultra gaming and oc it to 4.2 or i5 8600k with z370 mbo. The other parts of the pc are 8gb 2400mhz Rx580 8gb...
If you're already getting an 8th Gen Z370 motherboard, I'd recommend getting the i7 8700k for gaming/streaming because it has 6 more threads (good for multiple processes) and better clock speeds. It's considered the best processor in price to performance for gaming right now, and has room for extraneous processes like you'd need for streaming.
Removing the i5 8600k and just comparing the i7 8700k and the Ryzen 5 2600x, the Intel is maybe ~$150 more expensive (including motherboard) but many would say it's worth it for the increased performance you'll get.
Only comparing the i5 8600k and the Ryzen 2600x, it's pretty similar and ultimately it "depends". Still, I'd definitely go with the i7 8700k over either and there's a solid chunk of evidence to support this, but it's a little more expensive, like I said.
Prices are MSRP but here's the "average user" benchmarks for the 8700k vs the Rzyen 5 2600x (looks like some overclocking is factored in, too):
http://cpu.userbenchmark.com/Compare/Intel-Core-i7-8700K-vs-AMD-Ryzen-5-2600X/3937vs3956