Hi, My 2010 21.5 iMac currently comes with the stock i3 3.06Ghz, and I have read that it is possible to upgrade to an i5 3.6Ghz (i5-680, which was actually a BTO configuration for this model). I have found a few for about £60 on eBay. Is it worth the upgrade? I would only be able to re-sell the i3 for about £10. And how difficult is it? I consider myself fairly experienced, and have upgraded this iMac before but only to put in an SSD and extra RAM, but I don't want to take on something too difficult. Thanks, PS: Is the GPU at all upgradeable? I have read conflicting reports on the internet.