The memory problems are related to objects relying on huge texture maps for their shading (e.g.  Poser figures), and that's about it. Texture maps are memory hungry, a 4096x4096 image will use 64 megs of your ram, this is not only a Vue thing. Vue 6 has new options for Poser import that can further consume memory, and these options can be used or not. 
I have a 2.6 ghz P4, 1 gig of ram and a GeForce 6800GT. Never get the out of memory message ( honestly) with one Poser figure in the scene. Bringing more figures of course is another story. Your system specs are alright for Vue usage.