is there a particular reason you need your RAM at 1600? because there is no performance difference between 1333 and 1600.
I assume your overclocking is done by multipliers? How many sticks are you using? Try giving more voltages to CPU-NB?
I would leave it at 1333. Tom's did a test on memory scaling with phenom ii. The DDR3-1600 config won the synth tests, but 1066 and 1333 came out ahead in the real-world apps. Unfortunately all of the systems were within 0.5% of each other.