^ This right here. I actually recently made the same mistake, I originally had 16 gigs of Corsair 3200 CL16 and I bought another 16 gig kit to total 32 gigs. Big mistake. Now it was mostly stable but I did get memory errors in memtest for instance, and that's just no bueno. And, even if they turn out to be the same ICs, they can still have errors because they aren't a single validated kit of ram.

You always want to buy a single validated kit of ram, so if you want 32 gigs, either get a 2X16 kit or 4x8 kit, but always make sure it's one validated kit. I recently bought 32 gigs of Trident Z Neo and I haven't had any issues. For less headache you should probably try getting something that's on your motherboard ram QVL list as well.