Can someone give me the low down on the difference between the screen quailities of a 17" and a 20" iMac. I owned a 20" rev b for a short time and was very impressed with the screen. I want to know if the 17" screen is just as nice except smaller. I noticed that the brightness and contrast ratios were a little lower, but how much does that affect the quality? I'm interested in saving 500 bucks by going with the 17". I travel a lot so the 20" is a little big. Thanks in advanced.