If you don't want to overclock, there is no sense in purchasing a K version of any cpu, since the K means they are designed with overclocking in mind.
Just get a version without the K, that has the most desirable speed for your needs. Wouldn't focus to much on the i5 vs i7 debate, Intel recently releases the i5 6600, a beast on its own that can match any i7 apart from perhaps the top model.
Thanks for the reply.
Not OCing, that's why I didn't think of Skylake when there only were the unlocked i5 6600k and i7 6700K. As you say, the i5 6600 looks great, that's why I'm thinking of Skylake instead of Haswell refresh now.
Yup, I was not going for an i7 anyway, it's an overkill for what I need/want the CPU.
Yes, the expensive DDR4 memory.
Thanks for the answer!
Well, where I live, 8 gigs (2x4) of ddr3 1600 are around 50 euros, while 8 gigs (2x4) ddr4 2133 are around 60. It's not that much. So if that is the only reason, I'm definitely going with Skylake instead of Haswell refresh. Plus, ddr3/4 compatibility comes with the chipset. I could go Skylake and ddr3 if I were to buy a B150 chipset mobo.