Mixing and matching RAM does not always work. Even if you mix the same model and quantity. This is why RAM is sold in kits, because each kit is tested to work together. With that being said, it does not mean that it wont work, you just cant guarantee that it will. So it is worth a shot, but I would buy it from a vendor with a good return policy just in case it wont boot. You will have better luck trying to match capacity, speed and Cl.