Great.
I'm a fan of the history that Hornucopia has built. I found this handy when looking at some vintage horns. This may give you some ideas.
http://horn-u-copia.net/Reference/Produ ... t=Trombone
When I'm working on project in my day job as instructional designer, I try to think about "What is the problem I'm trying to solve?" If your focus is on horns that are currently available, there is a lot you can do beyond specs like bell size and bore. I think part of your success would be predicated on what kind of added value you present. As a consumer of this kind of info, here are some problems and features that come to mind that I'd like to see. Others can feel free to add.
*Some sites don't have the latest model or feature listed. Be not only accurate but up to date.
*Some sites have images but omit something important like how the trigger is set up. Images that highlight distinct features, and help identify a model from similar horns.
*Some videos are incomplete or biased by maker. Links to high quality independent review videos by pros and teachers.
*Sometimes I can't find the maker's promo material. Links to manufacturers promo video, which sometimes have quite good performances, are polished, but biased.
*Who makes this horn? Links to manufacturer's site.
A related technique is creating a
user's story, kind of in this structure: "I am a ______ and I want (to be able to_______". Designers like this format of problem statement because it does not a force a solution and is not limiting like a problem statement.
*"I'm a
serious buyer and I want
to avoid watching people practicing on new horns or videoing taking it out of the box, and wasting my time waiting for them to actually play the horn." One solution is to add a filter or limit really low level amateur videos, which have their place but don't typically examine in a way that shows the strength and weakness of the horn. This kind of feature would be a help to me to avoid the random stuff in a typical video search. Another solution might be to just add a clear description to videos, another is to add a rating system on key parameters like "quality of demo" "quality of info".
*I'm a novice and I want to buy a new Conn Constellation but I don't know if it is still made. One solution is to add year the model came into production, or year a feature was added. And note they year ending if a horn is out of production. Another solution is to categorize the listing as currently available vs. historic.
*I'm a teacher and I want to know about horns in a specific price range that I already have approved. One solution is to add some kind of filter or search. Add drop downs to filter by price, place of manufacture, etc., like a real estate site.
*I am a pro with a lot of gear and I want to share my experience and knowledge with others. One solution is to add ways for users to add content, like Wikipedia. I might want to add links to videos on manufacturing process by the maker. Others might like to link to their ebay post