BenMMusTech
I recently went through the whole computer upgrade thing, and here is my take. Firstly, always get the highest speed CPU you can, no matter what you intend to do with machine. Second of all, in reality, depending on what your mixing style is i.e. a large amount of plugins used versus not many...the most important thing to consider when buying a new PC for creative work is ram, graphics ram and future proofing.
Ben

Thanks, Ben. I agree, that's why I'm gonna get 7700. The rest of the system is quite capable of handling heavy loads.
 

abacab
Just to throw wrench into the decision making process, how about these Intel Coffee Lake CPU's?
 
The six core stuff looks pretty sweet! 
 
http://www.tomshardware.c...ces.html#xtor=EPR-8886

Well, that new core shows great results in CPU benchmarks. But in my case getting a Coffe Lake CPU would require a new MoBo and complete reinstall of OS and every piece of software. Not ready for this yet.

Soundwise
 
Well, that new core shows great results in CPU benchmarks. But in my case getting a Coffe Lake CPU would require a new MoBo and complete reinstall of OS and every piece of software. Not ready for this yet.

If you are running Windows 10, no reinstall required for mobo swap.

If you're looking for an 8700k, good luck finding one in stock.  
 

So long as you don't question yourself after buying the 7700 wondering if you should have maybe gotten the other one for the same price  I'm one to spend a bit more if it isn't much for a small  gain, even if I don't think I'll need it at the time. There have been times when I was glad I made that choice.

OK, thanks to all for sharing your thoughts and experience.
I have updated CPU from Pentium G4400 (Skylake 3.3GHz) to i7-7700 (Kaby Lake, 3.6GHz). Swapping the CPU went surprisingly smooth and didn't cause any trouble.
Have I noticed any difference? Well, yes and no. My system is fine-tuned for audio recording and ran remarkably well on G4400. The only difference is how many plugins Sonar can handle and how long does it take to render audio or video projects. That's it.
Was it worth it? I hope so. Time will tell.