Most all forums have a "classified" or "trading post" section but you'll be limited to the viewers of the website. For free the is usadiomart.com To get an idea of what a model sold for or if the same is currently being sold look at Hifi Shark - Used, Second Hand & Pre-Owned Hifi from 200+ Sources There is a fee based sell/buy site called audiogon.com Vintage is still enjoying bit of an in vogue moment so probably a good time to move it if you were going to.