I'm planning to buy 2x4GB strips of DDR3 RAM at 1600MHz 9-9-9-27 (see here) The box that it is going in will be used to run virtual machines. This means that I may want to stick another 8Gb in it at some point.
I was wondering if I could get another two strips of RAM at some point and they would still play nicely together in dual channel mode. Do I have to buy the same make and model or just something very similar? Which factors are most important?