I'm looking to buy new 21" iMac. System would be used for photoshop and illustrator type work. Is there a big (noticeable) difference in processors between what comes with the "standard" set up (2.7 GHz Quad Core Intel i5) and the upgraded version (2.8 GHz Quad Core Intel i7). With either set up I'd upgrade from the standard 4 gigs to 8gigs of ram. Thanks for the help and insights.