I'm still confused as to what the numbers even indicate and how that all relates to making an optimized system but after two hours of research and still not getting it I give up. Thanks calinkula going with 1600.
It relates to the speed of the RAM. Much like the frequency of a CPU, but it's a little different because of timings. Timings is how many clock cycles it takes for the RAM to respond to a request (lower is better).
Anyways, to keep it simple just go with some DDR3 1600 from a reputable brand.