I have a D300 and use it in the following way. I shoot my child dancing on a stage so action and low light. I know two strikes against me. I use my 55-200 normally with ISO on High. Would I be better with a fix lens? Any help would be great.
What focal length do you find yourself mostly using with the 55-200mm? If it's around 50mm or 85mm most of the time a prime lens in one of those focal lengths would handle the low light better than a fast zoom like the 70-200mm f/2.8.
The other big question is how much do you want to spend?
If you can do without the zoom, look at the 85mm f1.8 for under $500. But if you can move closer, the 50mm f1.8 is a bargain, and a very good lens.
Can you get the framing you want keeping your 55-200 at 55mm? If so, you'll be happy with the 50mm, and won't be spending too much to get it. (There's also a 50mm f1.4, for more money, but if you're price-conscious, the f1.8 will do fine.)
An 85mm 1.4D Nikkor is around $800-900 at KEH. An 85mm 1.8D is in the $300-400 range at KEH. They also list a 105mm f/2.8D Micro for $415. This might work for you at a slightly longer focal length and also give you a macro lens to boot.
Just keep in mind, if you can't move, you may need to use a shorter lens and crop longer range shots in order to cover the whole stage. That is one advantage of a zoom.
KEH does list Sigma and Tamron 70-200 f/2.8 zooms in the $650-750 range. Neither has their version of VR, but they are pretty good lenses.
Welcome to Nikonians! For shooting action in low light situations when flash is not allowed "Fast Glass" is the price of admission. If you are shooting at the wide end of your 55-200mm the Nikkor AF 50mm f/1.8D, 50mm f/1.8G AF-S are the least expensive options. The AF 85mm f/1.8D or 85 f/1.8G AF-S provide a little more reach for about double the price. The AF 80-200mm f/2.8D ED or the Sigma or Tamron 70-200mm f/2.8 lenses would be next if you need the versatility of a zoom and or the additional reach. Good Luck and Enjoy your Nikons!
As those previously have said, if you can get close the 50mm f1.8 is a great little lens. When my wife bought me one for Christmas a couple of years ago, she kind of wondered what she was buying for $150. I of course was thrilled. She said "it looks so small". I said maybe, but it packs a punch. Best $150 spent on my camera gear.