Laurence Brenner

The i7 will help in a fair amount of cases - If you can afford it, why not go for it? If not, the i5 will also do a very good justice for gaming.

The i7 is better at everything, for some things more than others, but the 6700K outperforms the 6600K in all tasks.
Hence, the only question left is how much are you willing to pay for the performance difference. $100 for 1%? $1 for 100%? We can't tell you how much you value the additional performance.

GTA 5, Battlefield 1 and Witcher 3 all show benefits of hyperthreading, that consensus is becoming old, i7 is actually now becoming the preferred CPU, ofc that is if the budget allows

I always see it like this. Speaking about the K models, on the i7 you can always disable hyper threading. which will lower temps and power consumption and still get the higher cache and clock speed. That heading from disabled HT means you can possibly get a decent overclock. I use to do that on my 4770k. I would disable HT because i didn't use anything multi-threaded heavy (like video editing) so i benefit from the headroom gained from disabling HT.

If you can fit the i7 without crippling your GPU definitely take it

It will depend on what you want out of your build: monitor? what resolution? Do you care for a massive SSD? How about a beautiful (expensive) case?
 
I would consider a 6700K not the highest priority for performance because it's 50% more expensive but at best 15% faster.

Yeah, but that benefit is by how much? and is it actually hyperthreading and not the larger cache or other differences? 
 

Clock for clock in those games and more it performs better, more importantly the number of "low frame rates" is also lower tending to a smoother gameplay. This is more prevalent now with the release of the 1xxx series from NV meaning games are now becoming more CPU bound than GPU bound. Take into account that DX12 prefers cores/threads this picture is only going to become clearer as time moves on, maybe even pushing us towards 6/8 core CPUs (eventually)

As someone who has gone through three gens of Intel CPUs, I must say the 6600k should be a better move for you. I have gone through a 2nd gen i5, 4770k, and am currently running a 5820k; I decided to upgrade to the i7 series due to my need to edit high resolution videos. If you are looking to build a gaming system with a budget, I'd get a 6600k and use the extra dough to get a higher end GPU. In today's fast paced market, your main bottleneck over time will end up being GPU power most likely.

dont buy the i7, unless you dont mind spending the extra $

If you want to push 144Hz I would definitely try to fit the 6700K then. And a 1070 or similar card (might have to tweak settings for 1080p 144Hz even on a GTX 1080 tbh)
 
If your monitor has Freesync or Gsync, I would definitely take advantage of that so you get tear free, smooth framerates.

Rare indeed, but this is what the reviewer means, look at the green and turquoise frame rates, they're bouncing all over, and look at the i7's brown/red, smooth

Q1, I've read January 17th for some things, but rumours and speculation

You should get 16 GB, but you can skirt by with 8GB if you don't do much else while you game. It doesn't matter what frequency you get as it barely affects performance.