Hi. I am wanting to upgrade from 4 GB of ram to 8 GB ram (or possibly 16) , anyway what my question was that i currently have a DDR3 1333 MHz 4GB ram stick and am upgrading it. Should i replace it and get a Corsair vengeance 2 X 4 GB or should i get the same DDR3 1333 MHz 4 GB and add it to my existing one. And how much of a performance difference would i see if i get the Corsair one. As i saw on a video of Linus tech tips on youtube , more ram speed only results in about 0.2 - 1 FPS improvement in most modern games like BF4. Thanks in advance.