Yeah, what Undying89 says - consider that there is likely a trade off and your timings will have the greatest effect - keep in mind the ram responsiveness formula; CL/Frequency x 2000 = response in nanoseconds. The trick to overclocking ram is to get the fastest response from the ram (which may not be at the highest frequency the ram can do)
There are no simple answers to questions like this since the CPU and motherboard play a part also, 1866MHz is not unheard of from a 1600MHz kit but as with all overclocking questions, the answer remains with you to discover
Yeah, what Undying89 says - consider that there is likely a trade off and your timings will have the greatest effect - keep in mind the ram responsiveness formula; CL/Frequency x 2000 = response in nanoseconds. The trick to overclocking ram is to get the fastest response from the ram (which may not be at the highest frequency the ram can do)