Old Capacitors dry out and drift out spec. That means your tweeter, mid range etc start playing frequencies they are not supposed to play which degrades the sound quality. Typically, the old ones are cut out and new ones soldered into the network. The Dayton 1% caps are solid caps, nothing exotic but are more than sufficient for normal playback.
Good luck to the OP with the sale, I think the price point is very much fair given the cap refresh and rare finish.