I'm building a new rig with Asus M5A99FX PRO R2.0 MB and either a fx8350 or 8320 Cpu. Will it run smoother with 1866ddr or 2133ddr? My buget is tight so I'm going with 2- 2x4 8gb for now if I get 2 more later on which will be 4 sticks, will it run at 1866 or 2133 or will it default to 1600?