As I’ve noted in other threads re Harbeths... the Hegel H590 is among the best amps with Harbeths and, as others have noted, Harbeth typically shows their speakers with Hegel amps. I use the H590 to drive my 30.1’s and 40.2’s, which makes them sound just like the demos in the YouTube videos - as good as it gets.
Though I would note that I recently tried the AR 5SE Preamp and 150SE amp - and they drove the Harbeths as well as the H590, and perhaps a bit better, since they add the air and tone of Class A tube amps - very life-like with great resolution and transparency.
Either setup is great with the Harbeths.