TJCS is correct, but just wanted to add that you may need to look at the timings of the memory and the voltage as well.
A lot of the 1600mhz RAM uses a higher voltage then the official spec calls for (I think the JEDEC spec is 1.5V, and a lot of 1600Mhz RAM runs at 1.6V or 1.65V). Think of 1600Mhz RAM as overclocking "regular" RAM.
Since you want to run it at a lower speed, you should be fine at the default voltage, but it is something you want to check to make sure it's stable.