I did an i7 build with 6 Gigs DRR3, 64b Vista.  Have been using it for about 2 weeks with Poser 7 and am VERY happy.  [Previously, a 2 year old AMD dual core.]

Renders are faster, but not lightening fast.  The huge improvement for me is the ability to handle 6+ figures with clothes and props.  Smooth as silk.  Never freezed, never looses textures,  never crashes - at least, not yet.