I owned the C7 es3xd for a while and can vouch it is a great speaker. When people say Harbeth's can play your favorite songs and make them sound great, believe it. There is a clear window into the music and it only wants to make you turn the volume higher (no fatigue).
The downside that I saw is that in order to get them to stage well and really disappear they need some power. Sure they sounded great with my 14 wpc tube amp but the control an amp needs to hold on the speaker made the tone great, but that's so much less than this speaker can do when supplied with 60 plus wpc. If you find a ss amp that you like that's fine. I really enjoyed the Supernait.
The drawback and reason I sold the C7's is twofold. First they wanted to be set up right- not particularly more difficult than another speaker but I didn't want to move them. I'd rather wrestle a mid size floor stander than deal with stands and spikes and top heavy situations. Second is recreation. They do great with smaller stuff, trios, singer songwriter and very good with larger music. Reason two, they get loud but don't really want to be pushed beyond. I'm responsible with volume and power and could hear them struggle and loose pace with other speakers I've had. Bass heavy music, tread lightly- Now to be fair the Supernait is like 85 wpc, maybe they'd do better with 150 per side, didn't try.
Good luck on your search. Part of the fun for me has been trying tons of gear over the years and I'm glad I tried Harbeth, and it's on my list to try again some day.