I think the Power Dampening feature is now available as an option of all of the Mojave product line, including the 100 Watt Peacemaker.

Any amp with a Master Volume control reduces the output; its just a different technique.

I think at least one of the Mesa amps has a built-in Variac to reduce the voltages on the power tubes. Note that this is set up in a way that maintains the full voltage to the tube heater filaments. Simply plugging a tube amp into a variac and rolling back the line voltage can trash every tube in the amp!