I have a stick of 256 pc2700 ddr and 512 pc2100 in my comp right now, i have an extra 256 pc2700 ddr stick but extra slot. Is it best to leave what i have in now and let it run at 768 pc2100 or take out the 512 and put the other 256 pc2700 in. Which would run faster, or would they run about the...