I'd suggest you consider the Anne Hills/Cindy Mangsen/Priscilla Herdman model-- three powerhouses who do some things together but not everything, who know what material suits them as a trio but have individual strengths as well.

Also consider the reality I used to hear a lot of my "pro" friends talk about-- the more people there are on stage, the less each one makes, as cover charges don't go up very far.