Do you want to use a differend rendering engine or do you want to have more control to Poser's Firefly renderer?

If you want the later, you will find advanced options in the menu:

[Scripts][Partners][Dimension 3D][Render Firefly]

If you want to use a different render engine for movies I would suggest you take a look at Vue, which can import Poser szenes and even keep the Poser materials when needed. No idea how stable this is when rendering movies, you might want to ask for it in the Vue forum. You will find Vue here. 

You can render directly into Divx if you have the codec installed. But usually it's better to render in single images and create the movie from them later. This way, you won't have to redo eveything if something goes wrong.

A ship in port is safe; but that is not what ships are built for.
Sail out to sea and do new things.
-"Amazing Grace" Hopper

Avatar image of me done by Chidori.