I'm going to buy my first ever Mac today, a 20'' model. I will use it mainly for domestic works (internet, office, musics, photos,...) Is the 2.66Ghz iMac worth the price over the 2.4Ghz model? Also will the graphic card in the 2.66Ghz make a really difference? Or it is a good idea to save $300 and put 4GB RAM in a 2.4GHz model? Thank you!