Try to stay away from Yachtworld. This site has an Albin Vega listed for 6K and a CD28 for 9.5K (both I believe are in Vigor's list of 20 small boats):
Sailboats for sale, Sailboat Classifieds, sailboat for sale by owner, used boats
You can find CD28's on yactworld for 35K, but if you dig a bit, they are privately f/s everywhere for 10-15K and often cheaper.