Hello, I got an iMac 2011 21.5" inch. and I currently got: 3 x 4GB RAM DDR3 1333MHZ RAMs and 2 x 2GB RAM DDR3 1333Mhz RAMs. What would be faster? 2 X 4GB and 2X 2GB. ( 12GB Total BUT matching slots ). OR 3 X 4GB and 1X 2GB. ( 14GB Total BUT no matching slots ). I just heard there's a need to be atleast two slots of the same amount or something like that. Thank you very much!