I have Sonus Faber Concertos (not the newer HOME model) which I power with my Classe CAP 151. This was a truly beautiful sounding setup.
Recently, we moved to a bigger house, and I got the chance to put the speakers on stands - instead of bookshelves.
I havenoticed that while they sound as beautiful and clean as ever on Jazz and Vocals, on rock, the Bass sounds tremendously overdriven if I give em even a little power. I use a Classe CAP 151 - plenty of clean power, never even gets above 1/4 of its potential.
Could they be too close to rear wall? Don't know if it is my amp or speakers.... both are 2 years old, and hardly ever really taken out for a POWERFUL drive...
Placement of speakers in the room is critical -- move them around, experiment. For some guidance, go to http://www.cardas.com/insights/index.html -- follow the link to "Room Placement" -- the exact formula offered may or may not work for you, but it's a good starting point.