That's a lot of coin for a very traditional, if well executed, speaker. If you're worried about the ability to fill your room, tha Salk SS 8 will have more dynamic range yet compromise nothing r/t the Harbeths.
It's been years since I heard a Harbeth, at RMAF, so take it with a grain of salt. The Harbeths are probably fine speakers, and for $18k they had better be! The SS 8 are among the best you can buy regardless of price.