Burlings Ton of Trains in Fountain Hills (just east of Phoenix) has been in business many years and has a wide selection of used trains in O, S and HO. He carries products from Lionel, MTH, K-Line, American Flyer, Marx with some Standard guage and G scale thrown in for good measure. It is one of the places I don't go very often, just to save my budget, but it is a delight with every visit.
Rolland