This may be a silly question, but I am wondering what is acceptable in terms of performance for the iMac G5. I bought the stock machine 20" screen, 512 RAM, 250 Gb HD. I know that a little extra RAM will go a long way, but I have noticed some speed degredation on simple tasks such as opening safari or even opening the hard drive to add an application to the correct folder. This has happened with iPhoto open, but also with nothing open. Should I be concerned?