kberke, Is there a way to get closer to the stage?
If not, I think Mike's suggestions to get faster shutter speeds without flash are going to be your best bet.
Ever see all those flashes going off in the stands at football or baseball games. Those flashes are doing nothing more than lighting up the backs of the heads of the people in front of them. My sb800 flash has a range of 30 ft(supposedly) and its one of the strongest on the market.
I don't know which cameras have stronger flash but its worth looking into but you'll probably also want to find a way to get closer OR you will have to go dslr which will help but its up to you whether you want to spend the money.