I am not familiar with Sonus Faber Concertino Domus but switched from the Sonus Faber Grand Piano Concerto to a Harbeth many years ago. i don’t have experience with the C7ES2 but have listened to the C7ES3. I don’t know how the C7ES2 compare to the ES3 but the latter was said to be a better sounding speaker.
Personally I would suggest to go with the C7ES3 if you can find a used pair. The Harbeth C7ES3 sounds more balanced, refined and detailed than the Sonus Faber. I find the Sonus Faber Grand Piano Concerto to be rolled off in the treble and lacks clarity and detail. The SF sounds overly warm but matches well with upfront and/or bright sounding amps such as the Krell KAV-300i. The guy who bought my Grand Piano Concerto uses a KAV-300i and the match between the Krell and Sonus Faber was pretty good.