I'm going to buy one of the new 20" iMacs and upgrade the memory to 2GB. I'd like to get some advice on whether buying the one with the 2.4 GHZ processor will make much difference over the 2.0 GHZ model, especially when it comes to using iMovie/Final Cut. I realize the hard drive is bigger and the video card is better on the more expensive model, but with the extra memory, is there going to much difference in the power of the iMac? Thanks.