In terms of simplicity, I'd stick w/ a single BES if you have less than 1000 users. Unless you watn a 2nd BES for Disaster Recovery (DR) purposes.

If you go the route of more than 1 BES, the suggestion of a consolidated Configuration Database is good. It make management and DR planning much easier.

RIM has a capacity planning calculator and performance whitepaper available at:

http://www.blackberry.com/knowledgec...se &sort=name