i think the biggest boon at this point for 3d stuff will just be the back end rendering functions. Kicking out work to the renderfarm.
Other things will take much longer. Okay aside from additional geometry being handeled better because of more ram and "elbow room."
But it looks like you can buy a license of Mental Ray now for 64bit EPIC Itanic architecture. I would be VERY curious to see how it performs versus its XEON counterparts. Intense optimization takes a LONG time though from what little i know about the more technical aspects of software.