Ok, I have a new i5 27inch iMac that came with 4GB memory. On a few occasions I've felt I needed a bit more. I will probably get my memory from OWC, and have two choices. 1. I can replace existing 2x2GB cards with 4 x 4GB for 16 GB for about $115, or I can keep existing 4GB and add 8GB more for total of 12GB for $58. I'm leaning towards just getting two more 4GB (8GB ) and upgrading to 12GB for $58, with the idea that 12GB will be more than sufficient for a while. Later (in a couple years) the price of two 4GB cards will likely come down and I can upgrade further then. My only (minor) concern is that I've heard that these memory are "dual channel" and you loose the dual channel aspect of the memory if you have mismatched cards (2x2 and 2x4) rather than the same size in all slots. NOt sure how accurate that is? If it is true, I'm not sure what that loss of dual channel will mean in practical terms, but I'm guessing for what I do, not much. Thoughts?