2nd Rick knows the drill. Most of us have learned it the hard way. But to me it's not clear that you are in a full on night club situation there. Sounds like you are in a pub kind of application with maybe a small dance floor on weekends? Define the scope and the requirements before you get involved.

The demands on a nightclub system and the requirements have changed dramatically in the last five years with the advent of hip hop. A system that could peel paint off of the back wall of a room is now inadequate in terms of delivering the low frequency people want to experience. Most clubs are either doubling their bottom end, or in the process of learning all about the costs of driver re coning.

When designing a nightclub system, remember this important word...."OVERKILL"
Build in a healthy margin of headroom or don't even bother.