Tom, you can't go wrong with either Nikon or Canon. Those two have been at the top of the game as far as image quality. I got the Canon EOS 50D in 2009 with an 18-200mm kit lens that has image stabilization. The 50D is the last still-only camera as far as Canon dslr's. Here is what I captured with it: 2009 DCI West.
Check out DP Review for reviews of cameras.
Keep in mind that dslr's are noisier than point & shoots. When I shoot from my seat, I try not to shoot during subtle moments in shows.