Help my band!

Edit Subject

I have a room (floor area approx. 4.00x5.00m) above my garage which I want to use as a band rehearsal room. It's already dry lined and plastered, roof space is heavily insulated and there are 3 double glazed windows. I can't afford to start remodelling the entire room, stripping off the plasterboard etc., but I really want to use the space. Cost is an issue, but the end result has to be effective.

Help?