That dealer has been trying to unload those mono locks for over a year now. I would run away as fast as I could.
One thing to consider, with 800 hours on the tubes, its going to cost a few grand to retube the units if you buy them from ARC. I think why they have been sitting for so long is huge the price to retube them when it is needed. It is a BIG expense. I hope you live in Alaska or Siberia as those amps will probably keep your house hot year round.
When I visit Audio Classics, they will set up anything I want to listen to without any fuss and after set up, leave me alone to enjoy. That is the kind of dealer you want. When I wanted to hear the Legacy Valors, they took out the big McIntosh speakers and hooked up the Valors to the 1.25kw McIntosh mono blocks with a smile and told me to"enjoy"..