Is your old gear fairly common? You could search current and closed auctions on eBay. They usually show everything at least 30 days back, sometimes more.
Search similar gear as well; for example "Kenwood Tuner" or "Marantz Receiver". You will get an idea of value, even if not your specific model.
Search similar gear as well; for example "Kenwood Tuner" or "Marantz Receiver". You will get an idea of value, even if not your specific model.