The photo images I work on start at 14 meg pix and convert to 128 mb 48 bit TIFFs for Photoshop.
CATIA (CAD) drawings are similary sized if not larger, many with over 256k worth of polygonal surfaces.
So yah, having a 2 socket, 4 core system where each core has it's own FSB into the ram and cache channels is damed important. The AMD 1000 Mz async hyperchannel helps a lot too. The key to the efficient use of fast CPUs is fast memory and fast disk on a motherboard with a fast chipset including the memory controller(s). If you're not willing or able to invest in fast memory and fast disk, then you may as well get slow CPUs too.
This is where Intels Core 2 and Core 4 chips fall down. Those chips share a single FSB with the on-board cores, the processors are basicly individual cores glued together inside a standard pin-count package. Each core has to fight the other for 'time' on the ram and cache data lines. AMD Opterons don't have this handicap due to the multiple interfaces to the hyperchannel and that each core has it's own memory controller.