Having retired and no longer using Photoshop, Corel or QuarkExpress, going to 'downsize' from my Quad Core Mac Pro to a new iMac. From users of the current series, is there any noticeable performance difference between the 2.5 and 2.7GHz CPU's? Would imagine not a great deal with some 7% difference in capacity. Also any noticeable difference in performance between the Radeon 6750 and 6770 gfx cards please? Thanks.