If you plan on shooting hockey seriously or for a living I would highly suggest investing In a better camera body. One that can handle higher ISO much better. If this is just for fun or for your kid then maybe try renting a F2.8 zoom or prime and see if you can capture the quality of images you are looking for with the camera body you currently have.
Most "better" camera bodies whether Sony, Canon or Nikon: all have noise at 1600 ISO if you compare images.
So a d7000, d700/800, D3S, D4 or sony/canon/pentax equivalents would produce the same amount of noise at ISO 1600 as the camera he is currently using? Yes they all have noise but I would bet a D4 @ ISO6400 would still look better than his current body at IS)800 -1600. But like I said if this is just for fun or the OP's kids games, renting a lens to see if he can get the image quality they want might be in order.
All I am trying to get across is that having an F2.8 lens vs a F3.5 lens with his current body might not help all that much shooting hockey.