Hello,
You could go with either
"CMT32GX3M4X1866C9" or
"CMZ32GX3M4X1866C10", both of them are good but you could choose according to your liking (there isn't much that separates these two except the different heat spreaders).
Personally I do not see the need for 32GB of memory. 32GB is a overkill.
Always good for future proofing your system. Have you ever come close on using more than 16GB?
It does help if you are using VMware or if you are just an overclocking enthusiast then you might wanna try it.
Good luck, mate!! adios