Depends on what you do with the rig, multi-tasking, video work, imaging, CAD, VMs, anything that's memory centric higher freq is better, gaming doesn't really require high freq DRAM currently as it's mainly used as a data conduit, but even in gaming 1866 will get you a few extra FPS over 1600 and a few more at 2133....with prices near the same from 1600 to 2133 and at times even 2400 would go with the highest that fits your budget