Poser can only utilize up to 4 cores.  If you check out Intels website it explains it better there, but a Core 2 Duo is a single CPU chip set  that has 2 processors built together so that the computer sees 2 CPUs.  The Quad Duo is simply 2 Core 2 Duo chips--so the computer and software see 4 CPUs.  Intel hasn't developed the architecture yet (though they are working on it) to build the 4 cores into one chipset.  Last years Dual Core Intel processors were simply 2 CPUs, independent entities working together, but not built together like they are now.  Graphics programs are the only software that really seems to be utilizing multi-processors, though it will have real performance value for the gaming industry in the future.    I don't know about AMD--but after a bad Athalon experience in the past I tend to try to avoid AMD processors and mother boards.  My laptop does have an AMD processor that seems to be decent, but I had a friend had a semprom AMD processor and it took a dump on him only a few weeks after he'd purchased it.