As far as professional grade softwares go, there is Poser-Maya plugin from Reiss-Studio (?). Maya is very expensive though. How many characters handled with terrains is RAM and processors I think, not software too much. More powerful machines can handle more stuff. :) Poser 5 has no demonstration versions, but Maya and Soft|Image do. Not sure where to link. Bryce I do not think is set up to handle Poser very well, but Vue d'Esprit is made to import Posers files natively, and has many features and benefits over Bryce. I thinks Vue 4 (?) costs 200 dollars or so.