Quote:

Or is the Newton one for people who have the commercial edition who want more than one object at a time?




Yeah, mostly. Commercial has the one physics object limit which newton does not...makes it an attractive solution for the Commerical Version user.

Quote:

If I upgrade to Pro (I won't be upgrading just for the physics) the would I need the Newton?




That's subjective. Feature wise, A6 can do everything Newton can and vice versa. However, some people say that Newton is more stable and that they like it better. I've personally not used Newton, but never ran into any problems with the A6 Physics Engines.

Thus, while it's not necessary to use Newton in Pro Version since they share teh same features, there is nothing stopping you from using it if you like Newton better.