@geofelt, I play a variety of video games, but from what I noticed my FPS usually drop with high anti-aliasing, shadows and NPCs on the screen.
Now, from what I've seen on the internet, intels i5 and i7 have worse parameters than i9. I'd like to purchase a CPU that would handle the most demanding games (incl. Total War series for example) and that would serve for years. I'll definitely wait for the next intel series, but I don't really see the point in buying i5 or i7. As for my budget, let's say it is up to 570 euro for a CPU (I'm aware that I will need to buy a motherboard as well).
First of all, anti aliasing is one of the more demanding settings for a graphics card.
You will likely not notice much difference if you reduce that setting. Particularly if you use a higher resolution monitor.
Intel I5. I7 and I5 perform essentially the same.
The first difference is how many threads you get. I5-10600K has 12, I7-10700K has 16, and I9-10900K has 20.
How many threads are actually useful in YOUR games?
Your 6700K has 8.
To see how sensitive your games are to the number of threads,
You can do this in the windows msconfig boot advanced options option.
You will need to reboot for the change to take effect. Set the number of threads to 7.
This will tell you how sensitive your games are to the benefits of many threads.
If you see little difference, your game does not need all the threads you now have.
The kinds of games where the number of threads makes a difference will be multiplayer games with many participants.
The second difference is what the boost clock is and how high you can overclock.
I5-10600K can boost to 4.8. That happens for a single thread when the overall load permits and the temperature is under control.
I7-10700K can boost to 5.1
I9-10900K can boost to 5.3
If you have multithreaded apps that can use many threads, then you can overclock.
How high is determined by your luck in getting a good chip.
I9-10900K is almost unobtainable in the US due to high demand.
And I9-10900K, in particular, needs very good cooling.
That means a well ventilated case, and a strong cooler like a top air cooler like a Noctua NH-D15s or a 240mm aio liquid cooler.
The higher priced processors are better binned and can OC to higher levels.
5.0 is likely for all three.
As little as a i5-10600K would be a nice jump over the 6700K.
Here is a review:
https://www.tomshardware.com/reviews/intel-core-i5-10600k-cpu-review
I might think a i7-10700K is as high as you would want to go for gaming.
It performs better than the i9-9900k and runs cooler.
Keep in mind that the graphics card is all important for fast action gaming.
Budget at least 2x the cost of your processor for the graphics card.