Very impressive amps! I’d be tempted as well. They are almost 20 years old and are likely on need of service. Does the original owner have any maintenance records from ARC or one of their authorized repair centers? In my experience ARC amps have large capacitors that need to be replaced at around 20 years. I had a D-115 that weighed around 85lbs and shipping it off for service was a bit of an event. It looks like these amps when boxed are 200lbs each. Does the current owner still have the original shipping boxes or crates? Can they be re-used for shipping?
Also, the previous advice to pair with an ARC pre-amp is on point. I like the LS 28SE and of course the Ref 5SE and Ref 6SE are highly thought of.
If that doesn’t dissuade you then you should absolutely go for it!