You can check out my reply to your post in the other blog.
There is just nothing that will work as well as Broadband radar that will be in your price range (reasonably fair priced)
There was one reply to your thread that always comes up when someone asked about radar and that it searching for birds. Which was never the intent of radar.
Nevertheless if you are interested in bird watching radar you would need an open array radar which takes you way out of what is reasonably fair priced and is really to big for a 25' boat anyway (in my opinion).