we have a 20" imac as a shared home computer that came with the stock 2gb of RAM. I'd like to up this at least a little, as using photoshop and other CS4 apps is a pretty slow task on this machine. I was planning on buying a pair of 2GB sticks to throw in the machine (it's a model with only two RAM slots) and then, started coming up with another scheme. what I am thinking of doing now is is buying a pair of 4GB chips, placing one in my MBP, and then placing the stock 2GB chip from my MBP plus the other half of the pair of 4GB chips into the imac, giving both machines 6GB of RAM. will i be losing out significantly on the dual channel performance? or is the difference going to be negligible.... It'll be more expensive, but will bump up my MBP in the process as well, which, though not hurting for RAM, could always use more.