If you haven't set the proper speed in the BIOS, then you should - as you are not getting the speed you are paying for.
Set the DRAM voltage to 1.65V (or 1.64 if it only goes up in .02V steps).
Set the latencies to tCAS=9, tRCD=9, tRP=9, tRAS=24.
Increase the memory multiplier so that the speed increases to 1600MHz.
You may need to set the "AI overclock tuner" to D.O.C.P, not manual, to get full control.
Run memtest to make sure everything is stable.
Ignore windows score as it is irrelevant.
If you plan on buying more RAM, you would be best off buying a 3x 2GB kit and remove your current set (should sell for a decent price). If you just buy another 3x1GB kit you will be occupying all 6 RAM slots, this puts a great deal of strain on the memory controller and might not allow you to run RAM at full speed and also will limit overclocking.