I owned them from 1978 - 90. They are a fantastic speaker, but require A LOT of power to get the best out of them. One of the most outstanding aspects was the external passive crossover which really brings them to the next level. Is it included? I was powering them with Crown DC300As, strapped in mono, for the tweeter panels, and a McIntosh MC 2350 for the bass panels. Some of the best low frequency reproduction anywhere, no sub required. I was living in Hawaii at the time and the tweeter panels ended up not working due to corrosion from the salt air. I ended up using the bass panels with some Bose 901s for highs. I really should have kept them, but due to the size, I ended up getting rid of them as I was down sizing. If they have not been exposed to coastal (salt air) environment, they should be fine. You might want to contact Magnepan to see if they can be repaired if, at some point, they should require repair. They really are something special.
