Upscale Audio in Upland, Ca has Opera and Sonus Faber.
The problem with the brand comparison you seek IMHO is that SF has changed its "house sound" pretty radically over the years. I've had a pair of Minuettos in my office for over 20 years and a pair of Cremonas in my living room for the last 7 or so. IMHO, the "romantic" sound of the SF line in the early years has been replaced by a much more neutral sonic signature of late.
The Opera line - on the couple of occasions that I've heard it - has consistently fallen somewhere in between, tho to my ear closer to the early SF sound.
I don't want to overstate that conclusion about the comparison of the two brands. It's more of an impression than anything else because my auditions were not extended, price controlled, or particularly focused. In the end, however, that was my take - FWIW.