16 GB is overkill for a gaming machine (in most cases, I know a few games like Star Citizen and Titanfall ask you to have 8 GB minimum, but those are the exception rather than the rule). Now if your doing a lot of virtual boxing or heavy on rendering (video or photo) I could see it as being an asset. I would start off with 8GB of 1866 CL9 and see how things work out. The nice thing about RAM, it's easy and relatively inexpensive to add more. Just make sure if you do you go with the same specs (not necessarily the same vendor, but that's a personal choice.)
Also make sure whatever you get is on the Qualified Vendors List. Sometimes motherboards can be very picky!
Edit: FWIW 1866 is good and as long as its rated for 1.5V using a XMP you should have no issues with heat. (I've been using some Crucial BallistX stuff for a few years, it never gets warm.)