Are you selling the receiver, tape deck, and speakers? The receiver won't get much because it lacks an RF input (which is sought after in this age of receiver). You might get a tad more than $100 for it, but no guaranty. The tape deck doesn't seem to be one of their higher end models. While it is a good tape deck, the market for tape decks is dwindling and people looking for tape decks want very high end models. You might get $20-40 depending on how an auction goes. You might get lucky on a private sale with the Tape deck.
The Maggies are hard to sell online because of how fragile they are. The shipping is therefore expensive and still no guaranty they will arrive at a destination intact. I would search among co-workers, friends, and relatives that have a respect for audio and will take good care of the Maggies for a private local sale.
This is a listing I found on Audiogon for the MG-1s
http://cls.audiogon.com/cgi-bin/cls.pl?spkrplan&1204897064
They may be hard to sell due to there age and size, maybe an audiophile will buy them for more than that price just for the nostalgia, depends on the condition as well.