I have Sonus Faber Elipsa SE speakers which are driven by an Audio Research Ref 110 with KT120 tubes. Audio Research is an excellent match with Sonus Faber. I would choose an amp that uses 6550/KT120/KT150 tubes and at least 100 watts per channel. If you don't have enough power the bass can sound a bit sloppy.
The preamp has more impact on the sound than the amp. But it is all about synergy. You want to choose components that work well together.