what the mother board can support and what the memory its self can be overclocked to without impacting the performance of the processor are 2 entirely different things.
do as slaymate said, keep your ram as close to stock settings as your overclock will allow you, so if you have 1600 ram, do your best to keep it at 1600. and to be honest, overclocking your ram will yeild ZERO performance increase in real world applications/gamming. you wouldnt be able to tell the difference between 12 gigs of 1066 to 12 gigs 2133 ram speeds. DDR3 ram is just so **** fast and effiecent, overclocking it really doesn't make any sense. itd be like making a downhill drag strip for top fuel dragsters.
also, dont forget to run the benchmarks in the benchmark threads before you do any overclocking... or else you wont be able to tell the difference.
also we need more people to particpate in the benchmark threads soooo.... go go go go!