Always prefer the newest Intel chipset. Not a fan on how they make so many different versions though. What's the point.
If i should upgrade today, i'll go with a Z170 chipet and throw in an I7 (Bang for the bug vice, you are better of with an I5 (as you know). Like the Core i5-6500. That's a good one for the money. I am just an enthusiast).
The other intel chipsets that doesn't have the 170 number after a latter, i don't care much for.
You can just as well go with a Q170 and H170, but since they are all priced similar anyway i go for the Z170 for the OC support. That's the main difference. Check out this link for chipset differences: https://en.wikipedia.org/wiki/LGA_1151
As a side note: The new lineup of chipsets and Skylake CPU's does also support DDR3. You just need a motherboard with DDR3 ports. So you are not forced to also buy new RAM if you already have perfectly good DDR3 RAM. However your motherboard options are more limited, because most of the LGA1151 boards uses DDR4)