Several thoughts come to mind:
- Is the floor sloped?
- Are you using theater type seating?
- What are the 2 areas behind the podium?
- How high are the walls?
- If sound is an issue, why not change the acoustical background or the design of the stage?
I have a design of a church that will seat about 5000 people, somewhat similar on the floor plan. It covers about 1 1/3 acres under a clear-span roof. Let me know if you want to see it, I am still redrawing it in SU from DeltaCad.