I have generic ADATA 2x4 1600 11-11-11-28. I'm planning to replace it with 1 8gb, most likely a HyperX Fury. My mobo only has 2 ram slots and I might another add 8gb in the future. My question is, what would happen if i use the 8gb stick in one slot and my old 4gb in the on the slot? Can that even work? If so, what do I get? Or is it just better to just use the 8gb and leave the other slot empty?