This is something i have been doing a lot of thought about lately. The low end i3 21" iMac would suit my needs for probably a year. The top of the line i7 would probably serve for three years before technology passed it up. I was originally going to go with the i7, but after seeing how well the year old lower end iMacs depreciate, I am starting to think i might be best to get a low end unit and sell it everyear and get a new one. Ideas?