Is the RAM swappable from an iMac (27-inch, Mid 2011) to an iMac (27-inch, Mid 2010)? Also, do you have to insert in pairs? It sounds funny, but we have an iMac (27-inch, Mid 2010) 3.2Ghz model at work and are wondering if we purchased a Mid 2011 model if we could use the RAM from the Mid 2011 model to put in the 2010. Giving the Mid 2010 a total of 4 x 2GB RAM. Then would purchase RAM for the 2011 to upgrade it - 2 x 4GB RAM.