" When I'm in Poser I Always like to view the scene in Full mode instead of FAST or BOX mode"

This, I believe would be a function of the RAM on board your Video Card.  I've always been told the RAM on a video card if for Display Purposes; i.e. let's say you are at one camera, and then switch to another, if your card does'nt have enough RAM to remember what the view from the first camera looked like, switching back to it will take extra time, because your computer will need to rerender the Preview.

The amount of RAM you need depends on; the size of your scene, how big you want to render, and then Render Settings.