I am not the windows expert at all - normally i would say, buy a Mac! Seriously, Vue on a dual processor machine only makes sense if you are doing a lot of animation work. Vue can only split work on several cpus for rendering animations (in terms of rendering a specific image of an animation on a specific cpu, not rendering one image on two or more cpus). So i would say, most important is RAM - as much as possible.

One day your ship comes in - but you're at the airport.