It's also a really good idea to attend a rally or two near you. Many rallies have "open houses" so that you can stop by and see a bunch of different trailers all at once. It helps narrow down exactly what you want.
For example, we knew we didn't want a big trailer, but we wanted a bit more room than a Caravel
. 20-21 feet just felt "right" to us - wouldn't have known without being in a bunch of trailers.
Otherwise, yeah - cast a wide net in your search. I finally found our Argosy by googling Argosy Minuet. It was on page 7, as part of the used inventory at an Airstream dealer...