The Z170 has some substantial improvements over the Z97 chipset. The Z170 now supports the 1151 Skylake CPU's, with an upgrade from DMI 2.0 to DMI 3.0 which supports a maximum of 20 PCI lanes from the CPU. This is up from the 8 lanes available from 2.0 and has greater support for the M.2 interface if you are looking for some great storage options. This also supports DDR4 which has double the density from DDR3. Allowing for 64GB of memory support. The Z170 also supports ten USB 3.0 ports instead of the previous six.
 
Ultimately waiting for the next chipset is up to you but there are some improvements worth noting.

In what way do you mean when you say the Classified K punishes you for running multiple GPU's? Keep in mind that the real world differences between x8 and x16 are around 1-3%. This makes any disadvantage nearly negligible for most practical purposes. You can see an excellent breakdown of this HERE.
 
It's also important to note that the Z170 has native support for PCI gen3. The Z97 is gen2 which means that an x8 slot on the Z170 is effectively an x16 from the Z97. Of course this is theoretical and real world results will not be identical, but this is one of the major improvements of the Z170.

If your chassis is constricted in airflow it is beneficial to use blower style high speed fans rather than the ACX style. The slot breakdown for the Classified K (for example) is as follows:
 

PE1 – x16, (x8 if PE2 or PE3 is used) lanes from CPU
PE2 – x8, (x4 if PE3 is used) lanes from CPU
PE3 – x4, 4 lanes from CPU
PE4 – x4, 4 lanes from PCH
PE5 – x1, 1 lane from PCH
PE6 – x1, 1 lane from PCH
 
As you can see, the appropriate lanes for use in SLI are PE1 and PE2. We do have the Z170 Classified 4-Way motherboard which has a PLX chip to distribute additional PCI lanes for up to 4-way SLI configurations. If you are only interested in 2-way SLI the Classified K is a great option as long as you have adequate cooling.

What is your game plan for the new build ?

Cool GTX
What is your game plan for the new build ?

 
Usage will be mostly heavy duty gaming and light productivity, in addition to the normal internet and video streaming stuff.  
 
Hardware wise I'll keep the 3 980Ti's, Creative SB Zx and the HDD's and SSD's that I currently have.  So the logical choice is really the Z170 platform, but I keep getting underwhelmed by it. 
 
Honestly,  I am doing this because I'm feeling lazy.  If I buy a new motherboard and CPU, then I don't have to disassemble my current PC for it's motherboard and CPU and then reassemble it with the Z87 board I have.  So, laziness and upgrade all at the same time.  

If I decide to go Z170, the Classy K is out of the running, the board doesn't really impress me. And the more I research Killer Ethernet, the more I think I want to avoid it. Right or wrong, that's just the impressions I'm getting.  If I could find the Classy 4 way, that would be awesome, but even the used boards on eBay are going for outrageous prices.  
 
Z170 boards Im looking closer at.
EVGA Z170 FTW (Still available on Amazon)
MSI Z170A XPower
ASUS ROG Maximus VIII Extreme (Stupidly overpriced motherboard)

And yes, aesthetics do play major part in my decision.  Some of you get the reasons why, some don't.
 
CPU would indeed be the 6700k.
 
I was indeed looking at the GSKill Trident Z Ram.  DDR4 2800 @ 32GB
 
Probably would not go with an M.2 drive as I've already got a decent SSD already.  Creative card will stay unless it doesn't play well with Window 10.  Oh yeah, I'm switching over to W10.  If I can't stand it, I've got Windows 7 to fall back on.
 
The other option I'm looking at is the X99 build.  
 
Motherboard yet to be determined.  Those in the running are as follows.
 
- EVGA X99 FTW K.  (can't avoid that Killer stuff on this one, plus it's hard to beat the price)
- MSI X99 MPower (Would have to use some plastidip on this one)
- MSI X99 XPower 
- ASUS ROG Strix X99 
 
CPU would be the 6850K
 
RAM would be DDR4 2800 as well.  Either Corsair or GSkill.  In either build, going with GSkill would be a new experience as I've always used and had good luck with Corsair.  But that aesthetics thing pops up everytime I look at the Trident Z sticks.
 
 
 
 
 
 
 

Vlada011
If you have option to buy i7-6850K IMMEDIATELY, INSTANTLY forget on Z170.
His 40 PCI-E lanes are more than i7-6700K+Z170 together. 
I feel very bad because I can't afford Broadwell-EX.
I bought X99 with plan to replace maybe processor later and extend life of platform.
I must think something after I upgrade graphic card.
 
 
But i7-6700K Z170 Classified-K 3200 DDR4 is best option for Z170.
 

I'm done looking at things for a few days.   Time to step back and think about things.  Maybe a few out of stock items will come back into stock.  EVGA - Hint hint. 
 
Price to performance advantage goes to the Z170.   Longevity and overall effectiveness goes to the X99.
 
 

Tempt me not sir!  
 
So much for stepping back and waiting.   Found and purchased an EVGA Z170 Classified 4 way.   Next up is RAM and CPU.

I over paid actually.  Not by much, but they knew they had something that is in high demand.   Not crazy pricing like the people on Amazon that wants 76,000 for the motherboard. 
 
And I will be going with 2X16GB sticks of memory.   Trying to decide between GSkill and Corsair.   
 
There is a very, very small chance that this deal could fall through.  If so... well, not sure what I'll do then.

Yeah.  My plan was to simply use the Intel port in that event.  
 

And you just succinctly summed up my feelings about it.    EVGA isnt the only one that's jumped on that bandwagon though.  

Memory decision will be based on a couple of things.  Aesthetics and price.  And yeah, I put looks above price, within reason.  LOL
 
 

Surprised you didn't wait for Z270 (Kabylake) which is due out later this year.
 

As i see it nowadays if upgrading to 1070/1080+ i see no point what so ever to ever get a x99 system since none of those cards support over 2-way sli :)

What you will go with X99. That's happy news for me as one of X99 owners.
To be honest between Z170 and Z270 situation will be very similar.
Maybe guys could buy better processor later for Z170, i7-7700k.
 
X99 is right choice and i7-6850K. Broadwell-E is my wish.
But I'm in process of decision between 950 PRO and SM961.
Now when I heard that NVIDIA will launch new Pascal series I could invest in M.2 first,
until new 14nm GeForce show up I will compensate minus in wallet. 
 
Did you choose motherboard? Now choice is excellent with many innovations.
X99 market have much better motherboards.