Mike Elliott is a brilliant designer but maybe not such a good businessman. I think that was Counterpoint's undoing. The SA 7.1, 5.1, 3.1 preamp series of the mid-80's were simple, reasonably priced and had great phono stages in them. I still have my stock 7.1 preamp, and while it's prone to microphonics and can be tube fussy, it still sounds great to this day.
To answer the original poster:
a 5.1, depending on condition, should fetch in the neighborhood of 500 - 750, while a 7.1 brings 300 - 375 (or more, depending how bad the buyer wants one).
To answer the original poster:
a 5.1, depending on condition, should fetch in the neighborhood of 500 - 750, while a 7.1 brings 300 - 375 (or more, depending how bad the buyer wants one).