Hi all, Can you use RAM that is a higher speed than was originally in there. Currently, my late 2009 iMac has 4 x 2GB SODIMM DDR3 1066Mhz. I'm struggling to find 8gb sticks that aren't 1333Mhz and above. Can I add RAM with a higher Mhz rating if I remove all the RAM already there? (I'm assuming you can't mix and match).