Upgrade to skylake

I'm in dire need of an upgrade and ddr4 seems to have dropped in price to the point where it's not at all unreasonable to go for.

Definitely going for the 6600k, but I'm still a bit undecided on the mobo and memory.
Thinking of the gigabyte z170 UD3, it's probably a solid choice but suggestions are welcome.

Memory is where I actually need help. I've kind of decided on corsair vengeance LPX (large tower cooler). But I'm unsure whether I should go for lower clock speed and lower latencies, or higher speeds and higher latencies.
My limited knowledge/instinct tells me to go for lower latencies, but the higher speeds are much pricier. Is that just marketing bullshit?

These are the (considerable) options in the store I'm buying at.
16 gig 2133 CL13 for €128
16 gig 2400 CL14 for €133
16 gig 3000 CL15 for €173

Get the 2133 and the lower latency you will be fine.

What are you upgrading from?

AMD phenom II 955 on an asrock 870 motherboard with 4 gigs of 1333mhz ram.

Honestly, you probably won't notice much of a difference between any of those options. The default latency and speed for DDR4 are a CL15 and 2133MHz. Personally, I would go for the CL14 @ 2400MHz, but that is mostly so I would superior because I have faster than spec on both measures. I'd probably go a step further and look for CL14 @ 2666 or 2800. But seriously... that's just me being spoiled.

Short story, get one of the cheaper kits and you probably would never notice the difference between any of them.