Time to upgrade my aging Windows Athlon system. I want to give Apple a try, more out of just wanting to try something new. I'm looking at one of the 20" iMacs. Without getting in to the glossy vs matte debates, am I going to see much of a performance difference between a white 20" refurb and one of the new aluminum 20 inchers? Much of a speed difference between 2.16 ghz and 2.4 ghz on the core duo's ? How about the graphics cards. White iMac would come with a 128mb X1600 card vs a 256mb HD2600 card. Not doing games, no video, just basic post-processing. Is it worth the extra $400 for the newer model?