I purchased the 16gb (2 x 8gb) kit from OWC for my Hex core. Previously, I read threads that discussed you may get better performance if installed in sets of threes (3 x 8gb)....but I also read that the real world difference would be minimal. Fast forward to now...I believe I read where someone said that if someone has 2 x 8gb sticks, and they try to add a third 8gb in the future that it "might not match". What does that mean? My plan was to buy another 8gb stick in about 9-12 months. Do I need to buy it now to make sure it "matches"? Also, as I understand, the 2 sticks need to go in the 1st and 2nd slot, right?