So I just purchased a new 2015 iMac. I would like to add some memory but would also like to leave the current memory in the system giving me a total of about 24 GB of RAM. I have two options, the first is OWC who can match the DDR3 1867 RAM perfectly but is more expensive or Crucial who uses DDR3 1866 RAM for less money. My question is can I use the crucial RAM in the system with the existing RAM?
