I'm sure this has been asked and answered before, but I have had no luck searching. I apologize in advance if that's the case. I just ordered a new 27" iMac and was wondering if I can add a single 4GB stick of RAM to the existing 2x2GB for 8GB total. I know that you can add 2x4GB for a total of 12GB, but not sure about just one. I would like to be able to have just 8 for now with the option for 12 down the road. If not, I'll just go for 12 off the bat. Thanks for your help.