I will soon be in the market to upgrade my computer (2006 Mac Pro) and I'm looking at the refurbished imacs. The prices seem reasonable but I'm confused about the processors. The cheapest is the 3.33 Core 2 Duo followed by an 3.2 Intel i3 and a 3 Intel i5. There is a significant difference in price between the i3 and the i5 and not a big difference between the core 2 Duo and the i3. My question here is there a significant difference in performance between these 3 processors and and especially between the i3 and i5 to justify a $150 difference? If there is anything else that I should be looking at, please let me know.