I currently have 4x8GB sticks from XPG Z1 288-Pin DDR4 SDRAM DDR4 2133. My motherboard is an Asus X99-A USB 3.1 that supports up to 8 DIMM slots (64GB), which means I have 4 free, and 3200 max speed. I am wondering if my current 4 would work with the CORSAIR - Dominator Platinum RGB 32GB (2x16GB).
mixing RAM, even if you get the same kit but at a later date as a separate purchase, is not guaranteed to work properly.
to absolutely 100% ensure that RAM works together, they must come in the same kit.
So if you wanted to add in additional RAM without replacing your current kit, then you are just going to have to try it out and see what happens.
If you get additional RAM that has a higher rated XMP speed than your current kit, then what will happen is that the new kit will only run at the speed your current kit is set to run at.
If you want to guarantee compatibility without taking any chances, then you'll need to buy a whole new kit.
And if you wanted to max your capacity while buying a new kit, you would need an 8x8 kit for 64GB of RAM.
So to say it again, when it comes to mixing and matching RAM that didn't come in the same kit, then it's just a trial and error sort of deal.