I'm considering buying an iMac and have questions. Context-- I'm basically going to use my machine for browsing. I don't play computer games, but I do enjoy watching YouTube videos. 4 questions-- 1: Will AMD Radeon HD 6750M with 512MB or AMD Radeon HD 6770M with 512MB cards play a role when watching YouTube videos? 2: When I watch YouTube videos the fans on my 2.4 GHZ MacBook (2008) go crazy (I assume flash is the cause). Will moving up to 21.5-inch 2.5GHz or 2.7GHz models make a difference? 3: I believe the new Quad-Core Intel Core i5 chips are 'cooler'. Does this mean I'll hear the fan kick in less frequently than my current 2.4 GHZ MacBook (2008)? 4: Did any of you move up from 2.4 GHZ MacBook (2008) to 21.5-inch 2.5GHz? Is the experience pleasurable? Thanks a lot!