If you thought it was 1066, then you must have left the divider ratio at the default 2:8 (such that 8 x 133 = 1066) because this is the limit of official Intel support, anything faster requires adjustment.  Setting it to 1600 is as easy as changing the divider ratio to 2:12 (such that 12 x 133 = 1600).  Just make sure the Vdimm (memory voltage) and timings match the packaging, and voila: DDR3-1600.
 
Note: Once you do this, trying to overclock the CPU will cause trouble since beyond 1600 might not be gauranteed.  If you wanted to enable "Dummy OC", which automatically locks a Bclk of 160MHz from 133, you might leave the divide at 2:10 (10 x 160MHz = 1600), then your CPU will go to 3.84GHz (24 x 160 = 3840).  Whether you need to raise Vvore or not is something you'll have to see yourself.  Dummy is supposed to be a casual overclock preset.