I seen on my motherboard specs it says this 4 x DIMM, Max. 16GB, DDR3 1800(O.C.)/1600(O.C.)/1333/1066 Hz ECC, Non-ECC, Un-buffered Memory, So that means the highest mhz it supports is 1800 rite? If I get the 1866 will it just run it at 1800 or likely to not work at all? Would it be better just to get the 1600Mhz?
The above link is from the mobo website.. download the PDF and you can see what memory sticks that were tested with this particular motherboard. Keep in mind your selections are not limited to this.. its just what they tested and knows 100% that works.
Knowing this, we can definitely use it as a guide in purchasing more advanced RAM sticks for your build. I am a huge fan of Kingston because they are reliable and stable and just work. Like any other RAM sticks out there.