Wanted to get some 'expert' opinions on an upcoming purchase of a MBP... I have a PB G4 now 1.67ghz, 1 gig or ram, so i know whatever i get will be a massive hardware upgrade, but i wanted to see which direction i should go. basically, i'm looking at the 13", specs: 2.53GHz Intel Core 2 Duo 4GB 1066MHz DDR3 SDRAM - 2x2GB 500GB Serial ATA Drive @ 5400 rpm SuperDrive 8x (DVD±R DL/DVD±RW/CD-RW) Backlit Keyboard (English) / User's Guide Final Cut Express preinstalled or the 15", specs: 2.66GHz Intel Core 2 Duo 4GB 1066MHz DDR3 SDRAM - 2x2GB 500GB Serial ATA Drive @ 7200 rpm SuperDrive 8x (DVD±R DL/DVD±RW/CD-RW) MacBook Pro 15-inch Glossy Widescreen Display Backlit Keyboard (English) / User's Guide Final Cut Express preinstalled beside the obvious screen size and speed, what are the major differences? are they worth $500? My use is mostly internet research, audio editing (nothing my current PB hasn't been able to handle with Garage Band), and some video editing (again, my PB has handled it well).... I'm not saying that i can't spend the extra $500 for the 15", i'm just asking what am i getting for the $$ and is it worth it? thanks.