I bought a 20" iMac last Nov. and am very happy with it. At the time I upgraded the RAM to 2GB, but I wonder now if I should have gotten more. Will it really boost performance, or just help with graphic intensive programs? I realize that I would have to replace both modules if I want to go to 4GB, so I was wondering if 3 GB is an option? Any thoughts would be appreciated. I was pricing the RAM out at Crucial, and the 4GB set is about $86. Thanks.