Thank you all for your responses.
Just to explain few things regarding my current situation, my motivation and needs....
I am aware the current i7 line-up is quite more powerful compared to the first i7 iteration - my CPU. Thats why i am considering upgrading in the first place.
I am not getting 4-core Skylake, even if it made most sense. After having six-core CPU for last 6 years, it would feel like a step-down - even if it technically is not, certainly not compared to 980x. Anyway, six-core for me. And since i dont want 8-core for 1000, if there is still 10-core, which is out of my league, i just settle for 6-core again. I checked Cinebench 11.5 scores and stock 6850k gets 13 points/OC to 4400 15...thats quite an upgrade to 980x, which gets 9,5 at the clocks i roll (3,78GHz)....and yeah, given my rendering background, i rate Cinebench as a CPU benchmark.
I dont really need it. What i need is new GPU - thats why i am going for 1080 or 2. I am going to use those for some archviz, so they are going to earn me some money and pay themselves back. Actually, i already saved some money for them this way.
I would love me some 1080Ti, but i dont want to wait another half year or probably even more. Already waited a year since last summer, when my previous GPU broke.
So going for a new CPU and mobo is mainly about enthusiasm for a new HW and pleasing myself. I cant really justify it rationally. I do the rendering with GPUs and as far as games go, i game nowadays only here and there and lets be honest, my current CPU is just fine for all the current games, including CPU intensive games like Ashes of Singularity. The GPUs are way more important for gaming anyway. And really, the games i probably played most this year, were Call of Duty: Black Ops from 2010, The Crew, which runs ok even with my current setup including mighty GTX580 and then game called Infinite Space: Sea of Stars, which would probably run on mobile phone.
But i still want to do it. There is one more thing to consider... i could wait another year or 2 and save for some proper upgrade (8,10,12 cores) in the future...but given the fact i am getting the GPUs now, at that point those will be obsolete again. So when i upgrade CPU at that point, still wont be completely satisfied cause of GPUs. And no, selling them and buying new by then its not an option. This is not big and rich country, where i live, so there ever wont be zillion of people lined up to buy my used HW at (for my) acceptable price.
Now the question is, which CPU? I read a bit, and it seems Broadwell -E dont OC as well as Haswell-E...so even 5820k/5930k might actually be options? I am leaning toward 6850k, since i rather new stuff and those 40 PCI-E links (and potentially higher binned CPU, so more likely to ask for less voltage when OCing?), even if RS says otherwise...if i go for it, I can spend those 150 EUROs premium... anyway, what do you think are the chances of 6850k OC to 4400? Anyone with any experience with these particular chips?
BTW, are these Broadwell six-cores cut-down parts from 8/10core, or native six-cores like my 980x? Out of curiosity, i could not find that info anywhere.
If i went for it, i actually consider buying AiO waterpump cooler. Which one would you recommend? Ideally not too expensive. I looked at Corsair Cooling Hydro Series H75 - is that good one? Another question is, will THIS and 2 1080s with their own AiO coolers (Evga Hybrid, MSI Seahawk) fit into my case, which is Fractal Design R2?
Finally, if i change mobo and CPU, but keep my disks, would the computer work or will Windows reinstall be needed? I had Win7 OEM, which i recently upgraded to W10.
Aww, bit of a litany. Sorry for that. Looking forward to your further advices.