I'm going to the Apple store tomorrow to buy a new iMac for when I go off to college in the fall. Should I buy the 17 or 20 inch? Either is in my price range and the screen space on the 20 is tempting for movie watching, etc. I also do some film and audio work in my free time which obviously would be easier on the larger screen. My main concern about getting the 20 is whether or not it will be too big for a dorm room desk? Thoughts? Feelings? ...