Heavv Graphics and Design?
CPU: Corei7 based processor
GPU: ATi Radeon 4xxx or 5xxx series GPU (Preferable a 4850 or higher or a 5750 or higher).
Why not nVIDIA? Because the 2D image sharpness and the color reproduction for nVIDIA is subpar at best (not what you want for heavy graphics). Both AMD and Matrox have the best 2D image quality but only AMD has the ability to use GPU acceleration in Photoshop out of the two.
Why a Core i7? Because it will offer you the best performance for demanding Heavy Graphics work. It is 2-3 years ahead (architecture wise) than any other architecture on the market today for such applications.