I am getting ready to purchase more RAM for my brand, spanking new PowerBook 15". What's the practical difference between adding 512 (for a total of 1 GB) and 1G (for a total of 1.5 GB)?. Other than digital photo editing, word processing, surfing, etc. I won't be doing anything hugely graphics intensive. (No games, movie-making, or powering large external monitors). I'm guessing 1 GB Ram would be plenty. But should I justt go buy a 1GB chip now?