Hi! I'm thinking about getting the 27" iMac. Since it's so much $$, I am considering buying a used model on Craigslist (my main uses for it is email and word processing, so i don't really need the latest and greatest in speed). However, i do want to be sure that the display is high quality-especially with things like glare and brightness. Has there been any display upgrades in the last 2 years of iMac versions that would make the display quality significantly better? In other words, should i avoid buying any used iMacs from the last 2 years because the newer version has a noticeably better display? Thanks a bunch!