When you get into that kind of age, I think you need to start worrying about the driver surrounds, caps in the crossover, etc. Still, if you're prepared to deal with that, it's a possibility. To me, it seems that when you venture into this area, you're moving into "enthusiast" territory.
There would only be a couple of classic models that would tempt me, like the B&W 801's, or the Vienna Acoustics Mahler's.
I didn't see any Avanti's on U.S. ebay.
Perhaps you need to start over with a new, specific thread (max budget, 3-way, floor-stander, being driven by X, in Y-sized room, etc.).