some help please...not sure about which iMac to get - i am am new Mac user. looking at either the 27 inch 2.7 GHz with 4GB RAM (512MB graphics card) or 27 inch 3.1 GHz with 4 GB RAM (1 GB graphics card). $500 NZ difference between the 2. can i upgrade RAM later? i am doing some photo and music editing - also want to run final cut pro x when it comes out in june so the machine will need to run this and Office for Mac amongst other basics. i am not gaming.Tech wisdom gratefully received! thanks all.