DONT PLUG THEM IN! They need some care before powering up on a Variac. With that said, look around for Dynaco ST-70 to get an idea. These are great amps but most likely will need restored. You could get anywhere from $200 to $700 each depending on condition.
As Jjrenman said, the tubes could be worth a bundle. If you take these in for service, don't let them keep the tubes if they tell you they are no good...