I have a 27" iMac Core 2 Duo, 3.06Ghz I think. I use it for Photoshop digital matte painting, as well as ZBrush. Will I see better performance if I upgrade to the current lower end 27" iMac 2.7GHz quad-core Intel Core i5? Worth the upgrade? Don't want to spend too much since a refresh is due within a year but my iMac is crawling.