Motherboard rated ram is 1333 and 2000(O.C.)?

Solution 1:

• Yes, OC stands for overclocking
• Of, course you can use 1600Mhz RAM (If you RAM supports it)
• No, there is no difference between 1333Mhz and 1600MHz you will notice. See this chart link.(It is german, nevertheless you will understand it.)
• Never forget timings, they matter as much as speed does.

The most important question is, if your motherboard supports the RAM module you want to use in general. You can check that on list from the asus link you posted or on several forums on the internet. (You will see that the PDF even lists 1600/1866/2000 Mhz RAM.)

Solution 2:

DDR3 2000(O.C.) means that you can use a DDR3 2000 on your motherboard but you have to set the speed/timing and other RAM settings manually in the BIOS. Otherwise it will just operate at the 1333 speed (down clocked)