okay so I bought a prebuilt and have been adding onto it for a while now and I need to get some more ram the ram I have now is 2 4gb adata ddr3 1600 sticks I was thinking about getting 2 8 gb sticks of 1866 speed to throw in there too would that be possible? my mobo is a gigabyte ga990fx gaming sli my cpu is amd fx 8350 and my gpu is msi radeon rx 470 8gb all suggestions are welcome! thanks! my mobo also have 4 ddr3 slots