I'm considering getting an iMac Core i7. I know the Core i7 uses multi-channel ram to increase memory bandwidth. Can anyone tell me whether or not you get the full speed when using a mixture of different sizes of ram in different slots? On my work computer (a PC i7) I have 12GB of 6 2GB modules. Having all the slots full meant having maximum memory bandwidth. If I got the iMac with 2x2GB ram to start with and then upgraded by adding another 2x4GB ram, would I still be getting the full memory bandwidth. Or do you instead need to have the same size modules in every slot in order to get the full parallel memory channel usage?