My partner is looking to buy a refurbished iMac from macofalltrades, and I am trying to give her to best advice possible. I am not in any way familiar with Apple products, so your advice will be incredible helpful! She is on a tight budget, and buying a new Mac is out of the question. She will not be using the machine for any heavy lifting, but we are looking to get a machine that will last a while and work with any OS/software upgrades released by Apple in the foreseeable future. We have, I think, narrowed down the choices to these two machines: http://www.macofalltrades.com/iMac-21-5-inch-3-06GHz-C2D-Late-2009-p/im-215-306-l09a.htm http://www.macofalltrades.com/iMac-20-inch-2-66GHz-C2D-Early-2009-p/im-20-266-e09a.htm What are the substantial differences between the two? The Late 2009 is currently $100 less. We are considering upgrading to 8gb of RAM. How will these machines run Mavericks? Is the processor speed difference significant? The hard drives? Would the following model ($200 more) be a significant upgrade?: http://www.macofalltrades.com/iMac-21-5-inch-3-06GHz-i3-Mid-2010-p/im-215-306-m10a.htm Any and all advice is welcome. Thank you for your help!