I'm planning to buy a new 20" iMac. I'm just trying to decide between the 2.0GHZ model and the 2.4Ghz model. Is the processor speed and the graphics card really a big difference? I would like to save the money if I could, but also don't want to cut myself short on what I need. I will use it mostly for iLife stuff (iweb & iMovie especially). I also plan to run a couple programs on Windows XP using Parallels. I don't game nor do I do any 3D graphics stuff. Any advice?