I currently have 4Gb (4 x 1Gb) installed in my new (2008 model) mac pro. I would like to upgrade to 8Gb, but would also like to allow for further RAM increases in the future - so would prefer not to purchase another 4 x 1Gb. If I understand correctly, the ideal memory configuration is 4 or 8 modules. What I don't know is whether the "imbalance" of having 6 modules would outweigh the benefits of an additional 4Gb; I find it hard to believe that it would. So, my questions: Would it be a such bad idea to purchase 2 x 2Gb right now, to add to the 4 x 1Gb I currently have? (That would allow for an additional 2 x 2Gb at a later date.) If I do that, what is the best way to install the 6 modules? (My impression is that I should keep the 4 1Gb modules as currently installed, then add the 2 x 2Gb in slots 3 & 4 on the top memory board - but am not sure about this.) Many thanks in advance for any advice!