I have decided it's almost time for me to get an Intel desktop Mac. BUT, the thing is, I want one that has a good processor and graphics chip/card, upgradable RAM, a SuperDrive and audio input. I don't want to spend more than $600 on such a model, and I'm trying to aim for 20" to 21" in screen sizes. A model made between early 2008 and late 2012 would be good. I plan to do quite a bit of photo and video work on this iMac, and I am hoping it would be at least a bit faster than my mid-2009 MacBook. I'm kind of right now aiming for either the early 2008 or early 2009 20" screen models. Any recommendations?