See if you can get the guy to tell you the price of the amps when new. If they are still reasonably current and in very good to mint condition then offer %50 of new retail and go from there. If they have cosmetic issues or are outdated then offer less. If almost new offer more like %70.
Your best friend here might be the Audiogon Blue Book which you can subscribe to for a fee . Inm your case you should really do that. It costs some money but should be worth it.
Your best friend here might be the Audiogon Blue Book which you can subscribe to for a fee . Inm your case you should really do that. It costs some money but should be worth it.