Unless you're outputting to 3DS , OBJ and the like, you won't be able to paint directly onto a Poser figure.

The ONLY reason I can see you wanting to get Extended is because on top of the 3D texturing capabilities, it have an official video timeline - basically another version of After Effects (if you don't own AE, and aren't planning on it). What this means is that you can introduce motion objects into your images, with all the fine tuning and Tools capabilities of Photoshop per frame.

Example - let's say you have someone firing some form of, say, plasma rifle at another character. You can load the image onto a timeline that is only for a few seconds long duration - put the plasma discharge at the base of the rifle and set a keyframe, then go forward maybe 3 frames and keyframe the discharge to be have whizzed way past the other character. Scroll back to the in-between frames, and render out the frame where it whizzes right past the other character's head, and you will now be able to have realistic motion blur for an action shot.

Youo can make camera motion blur, stuff like that - which would make it look out of a movie, and not just a 3D render.

Get the idea?

But you can also do something like this with some motion blur in regular PS - doesn't quite look the same but most people won't care.

Did that make sense?

Hope this helps-
-Lew ;-)