Hi newcomer and welcome to the Tom's hardware forum.
Your RAM is fine. Why?
1- Your mobo only support 1600 with OC, that in your case is set all the specifications of your RAM manually in the BIOS.
2- DDR means double-data-rate, the double means that you need multiply by 2 the speed that CPU-Z report, in this case, 2x668MHz=1336MHz that is the normal 1333MHz RAM.
Thanks, if I overclock to 1600 will games (crysis warhead) benefit from extra speed? and how can I do it safely?