My old Power Mac G5 just died on me a few hours ago, spurring me to finally get one of the new mac pro. I have been reading the threads on here about them, and was curious if the processors would be upgradable after you buy the computer. For instance, if you get a quad core, can you only ever upgrade to higher quad cores, or could you potentially put in octa cores later on? Even simpler, if I were to buy a 2.26 octa, could I (easily) buy faster processors later and put them in? If so who would I probably end up buying them from, apple or a 3rd party? Thanks for your help, just starting to get into upgrading my own machine.