I have a Late 2010 27" iMac with 12GB (2x4GB) and (2x2GB) of PC3-10600. I stumbled upon 2x4GB of PC3-8500 and was thinking about swapping them for the 2x2GB. A user on this forum said you could mix the RAM but the PC3-10600 would operate at 1066MHz. My question is should I install the RAM? Would it be slower or faster?