For anyone to be able to answer your questions, we would need a little more information. Condition isn't everything, but, it is a lot. A Silver Hawk in good condition is much better than an "OK" gun. The build quality will at least equal, or, more likely, exceed that of the 686 guns you own now.
The issues you had with the Beretta pump are not relevent to a discussion of Beretta SXS or O/U guns. That pump was a Manufrance product, if I am not mistaken, and was sold by Beretta, Colt, Montgomery Wards, and others.
Why don't you ask the seller what he wants for it? If the price is anything less than 1K, for a gun in good condition, it is a great deal.
Best,
Ted
