I am planning on upgrading my PowerBook G4's memory but I do not know what a good amount is. Currently I have 512 MB and it is a little sluggish. The applications I want to run include all of iLife (except Garageband), Office 2008, iWork, Safari, Mail, and some other small ones. This is on Leopard. Would 1 GB be plenty or should I get 2 GB? Do the two sticks have to be the same size? Could I add a 1 GB to my current 512 MB or would that be bad?