Hey dear iMac users, I read that you can change the gfx card on the 24" iMac. Can someone who owns one, confirm this please? And.. If I choose the 2.16GHz CPU - can I later upgrade to a 2.33GHz or higher? I know for sure you can upgrade HD and RAM.. Thanks so much in advance, dear mac users. I so look forward to owning a Mac!! Best Regards / Brian J. N.