You can ask what it might be worth in D&S, you just can't say why you're asking.
You can advertise it for sale in the Members Classified and Partswap Forum, or, if you become a Subscriber, in Barter Town.
Generally, since an amp such as a Citation II can be worth a significant amount of money, making certain that it works and works well is usually going to bring a much better price than it would if you were essentially saying: "You pays your money and you takes your chances.".
Good luck.