So gaming at 1080p. Got it.
Once you hit the i5 level, CPU speed makes very little difference in gaming performance at higher graphic details because the GPU is the limiting factor. ( see
here and
here for examples ) Being able to OC your CPU usually costs $100+ extra ( more expensive CPU and mboard, + aftermarket cooler ). Spending $100 extra for a couple extra fps is generally not seen as worth it.
If you play a lot of simpler games like WoW or LoL, then the CPU comes into play more since the graphical load is lighter. However, if you're already pushing 100+ fps with maxed details, getting 110+ fps probably isn't a big deal. So unless you're regularly going to run tasks that use the entire CPU, like heavy video editing, file compression, or professional apps, you won't get much value return on OCing the CPU. If you want serious game performance, you'll see better returns by spending that extra $100 into a stronger GPU. If you know this and still want a K CPU, hey, more power to you.
I also agree with Zerk that getting SLI/CF "down the road" is usually not a great option, especially with mid-range cards like the 480. By the time you get the second card ( let's face it, computer upgrades usually get delayed longer than we expect ) your GPU is a generation or two behind. At that point, I would rather have a newer card with better tech instead of doubling down on an older card. And thankfully with the massive gains we've seen in these new gen GPUs, you can max out 1080p and 1440p with single cards cheaper than you can with multi-GPU setups. Again, if you still want to, that's your call. Just giving you some facts and recommendations.
So, with that out of the way, are there any mboard features you particularly want that you haven't listed? Built-in WiFi? M.2 slot? I really like ASRock and MSI right now. Asus has great boards too, but you tend to pay extra for them. ASRock's Pro4 ( not Pro4S ) and Extreme4 lines tend to be feature-rich for a good price, so start there. If you want to OC, then you'll need a Z170. Otherwise, look at B150 and H170 boards as well.