Confused about Memory

I am putting together a new system and have most of my parts picked but I can not figure out which memory to get. I tried reading up on it but everything just confused me more. System will be--

Intel I5 2500K
Asrock P67 Extreme4 Gen3
Windows 7 pro 64
Nvidia GPU of 570 or 560-480 in SLI

My choices for memory comes from the Asrock list. But speeds and volts do not seem to be translating to me clearly. Someday I will OC my CPU and GPU. Does this mean I have to have memory that will OC also such as 2133? Or I can just go with 1600?

For 2133 is 9-11-9-28 or 7-10-7-27?

For 1600 I have see 1.5v 9-9-9-24, 1.6v 7-8-7-24, and 1.25V 9-9-9-24?

Is the 2133 memory really needed to OC CPU or GPU? Will it give me any real benefit over 1600?

Thanks

DDR3-1600 (100 BCLK at a 2:16 FSB : DRAM ratio) w/ decent timings and low voltage like the 7-8-7-24 kit you mentioned is for the most part the norm unless you're into benching, when higher speed modules like DDR3-2133 might benefit your score.

redduc900 said:

DDR3-1600 (100 BCLK at a 2:16 FSB : DRAM ratio) w/ decent timings and low voltage like the 7-8-7-24 kit you mentioned is for the most part the norm

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I'm shopping for 2 x 4GB DDR3 memory also, but every, or almost every 1600 speed module pair I've seen has a 9 9 9 27 latency.

Should I look harder for something faster?