One thing you should consider is getting a line in on the mixing board during the show and then mix that together with your live recording from in front of the stage. Talk to the soundman and see if he'll let you plug an iPod or something into it to record off the board. You won't get the crowd noise, but the mix will be much better and you won't have the audio volume distortion that you will get when trying to record from the crowd. Mixing them together later will give you some crowd noise (cheering, etc.) mixed in with a much better live music recording.