It's EXCLUSIVELY related to gaming.
Most games now don't make much use of multiple cores (WoW is a very special case of this) so HT that is active on the i7 doesn't bring any perfomance improvement. like AT ALL. You're spending 100$ more for something you'll never make use of, while you could use them for a better GPU/PSU/Whatever else.
i5s are exactly the same as i7s, but without HT. Until you run them stock, clock speed is not an issue and they can run exactly the same.
Basically, it's all about perfomance/price ratio, in which case i5 is definitely a winner.
Again, it's just a gaming discussion. If you add multitasking/streaming/workload = making actual use of the additional cores then we enter another realm and then an i7 should be better.
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Well, i don't want to attack you - so take this with a pinch of salt. But you got straight for overpriced components in some cases that doesn't give you anything for the additional value. Though it's your own money and if i had the availability i would have done the same because i could.
Example: the 8086k is just a binned 8700k. It's literally the same processor, just with another stamp. You could have save 120€ just on that. Then 512GB+1TB NVMe is just overkill, plus NVMe has negligible perfomance increases. I'm all for SSD-only systems, but 600€ of drives are just not needed, especially with the 1TB one which is storage i suppose.
The rest in the end is on line with current prices, you got the top line GPU, ram costs way too much now, so you cannot really make a deal on them; same for mobo since you got the top tier. All in all it's not a bad setup at all, you just went over the top on a couple of things.
EDIT: you could have spent a little less on GPU since ASUS has become the Apple of pc components - the quality is top tier, but also the prices that reflect more the ROG brand than else. But again, i buy Strix GPUs too because they're just good.
I'd like to see a photo of the build