cpu support 1333-1600.so you wont be able to reach higher clock speeds.look for lower clock latency.
if you look at the guide that came with the motherboard it says limited bue to chipset.
the memory controler is intergrated in the cpu.
look for dual chanel memory with the lowest clock latency cl at 1600.
the best will be 2x4= 8gb of 1600 mhz with a clock latency of 9 the lower the clock latency the faster the memory.
if you look at a 1866 mhz you will se it has a higher clock latency like 11-12.
the preformance benefit will only be 2%.
how much memory do you want and what motherboard do you have?