An older BB says retail was 3K, used value is 1557, wholesale mint is 919 and wholesale avg. is 515. I believe Sumo has some faithful adherents, like ADS or SAE. But the greater value lies with those aficiandos, and probably not the general marketplace. This is why the BB shows values for the various segments of the market.
Any speaker is going to take some RE, short of wall-mounting which perhaps you should consider. If you reside in a large metropolitan market, then a local sale is possible, always a good thing with fragile, bulky items. One more point is that these seem to be pretty rare. If the condition is good or better, you may be able to command a higher price. Good luck and let us know how things go for you.
Any speaker is going to take some RE, short of wall-mounting which perhaps you should consider. If you reside in a large metropolitan market, then a local sale is possible, always a good thing with fragile, bulky items. One more point is that these seem to be pretty rare. If the condition is good or better, you may be able to command a higher price. Good luck and let us know how things go for you.