If you should prioritize, I recommend focusing on RAM more than processor speed. Both are important, but Poser appears to benefit more from increased RAM (providing that the OS can handle it, NT/2000/XP takes better advantage of a RAM upgrade). I haven't received Poser 5 yet (I live in Europe...) so I can't give you any comparision between Poser 4 and 5 performance on my machine, but as a general rule it think what I wrote above still applies. I run a 2.2 GHz P4 with 512 Mb RAM on Win XP. Despite the fast processor, Poser 4 still begins to choke when I render too many figures with high res textures and bump maps in the same scene. RAM must be the only cure for that. Poser 5 with lots of strand based hair and dynamic cloth probably puts similar requirements on the machine.