I'm assuming you are fly fishing? Check out www.bluequillangler.com
Go to Pat Dorsey's Stream Report on that site for current flows, hatches, etc on most of Colorado's gold medal waters. You can also give their shop a buzz and ask questions -- they are good guys. Expect company on the river in any of these spots. At least after checking that out you will have an idea of some of the prime fisheries, and you can spread your search for lodging, etc from there.
Depending on when you are coming out, you may still be in the runoff season in which case you may need to find a tailwater.
Hope that helps.