A good place to sell is eBay
You can put it on auction. You can put a minimum price you will accepted and a "Buy It Now" price. Another possibility is to donatae to Goodwill or salvation Army and take a tax deduction.
However, it might be worth more than you think.
I still have an older Marantz 1060 power amp that still works great. I think it is worth about what I originally paid for it over 30 years ago
I still have a Fisher Audio Studio Standard AM/FM tuner that also bought over 30 years ago becuase it was the first digital tuner I saw. About the same time I put a digital clock in my Alfetta GT car. I had them in my garage system until I upgrade all my systems about two months ago. The Den was upgrades and the den equipment went ot the media room and the media roopm equipment went to the garage and I finally threw out my old off-brand speakers
in which some of the nine 41/2 paper cones were not working anyway. It was a 9xx and the "nine" in the name came from the nine direct/reflecting speakers. I don't know why or or how I thought 4 1/2 speakers could produce a decent sound spectrum.