After complete satisfaction with my 80GB Classic, and iPhone 3G (minus AT&T's shortcomings), and a real dislike of all things Windows based, I have made the decision to switch to Mac(intosh). And Im actually pretty excited about it. *Que Applause* So here is my question: Im going to buy the 21.5" iMac, pretty much all stock. And I will upgrade the memory when it gets here, as everything I read says having Apple do it with Apple (Samsung) memory is crazy expensive, and it is. So I went to a well known 3rd party memory vendor to see what they reccommend. They want to sell me four 4GB DDR3's for a total of 16GB. And I understand that there are four slots, so this isnt a problem. But my real question is, Ill already have 4GB from the factory, so dont I only need 12GB? Or is there an issue (I wouldnt think so) with mixing like memories from different vendors? And, as I understand it there isnt an option to upgrade the graphics card in the 21.5"? And if I can, is it worth my time and money to upgrade that card as Im not really a gamer, but I do run *gulp* flight simulator X from time to time. Thanks in advance for your time all. And Since Im new, feel free to offer up ANY advice for a new Mac user. Oh, almost forgot, is there any tangible benefit to drive the 45 minutes to the apple store and get this thing over just ordering from the online store?