Visiting Gene Gast is very worthwhile, he has a music store in downtown Bettendorf, Iowa. He has one of Bix's old horns and also has an interesting story to go with it! You need to give him some lead time however.
I also shouldn't have ranked the Library as low as I did, it's very worth while and a lot of work went into accumulating the materials. I truly find all of the sites interesting and it's hard to rank them.