i recently upgraded one of my computers to amd 64x2 4800, 4 gigs of ram and installed the windows xp64 pro operating system.  i have never had poser render so fast and it certainly handles complex scenes well.  i have kept as little as possible on this system...when i check in with task manager it shows lots of great memory use and is fast!  i also used the 'hack' that is shown elsewhere in the forums.  upgrading to the 64 os was really a challenge, and i'm still discovering drivers and other tools, but the whole process seems smoother than on my other machines.  the prices on 939 processors are very good right now, and although my system is'dated' from the onset, i feel comfortable with it.  the vista os looks like it has a lot of bells and whistles that are bound to grabbing valuable resources, so the gains in ddr2 might end up being a wash.