I am planning on upgrading my PC's graphics card, PSU, and ram. I have 6gbs of ram right now(1x4 and 1x2). I am planning on ordering 2x4gb pack. Should I just run 8gbs or should I run 12gbs in flex mode (8gb dual channel and 4gb single/ 3x4gbs ). Is there any drawback from flex mode other then...