Im in the same boat ... currently with 2x512mb in dual channel with 2 slots open. I'd like to increase the amount of memory, but I'd also like to stay in dual channel. What Im hoping to do is save up my money to get 2x1gb sticks. Probably buy one now, sacrifice dual channel for a short time, then buy another to return to dual channel. 3gb is overkill in this day and age, but when I get the second stick, I'll think about transferring the 2x512mb, to a new machine. However, my goal of maxing out my memory to 4gb will be reachable with 2x1gb and 2 slots open.