If you want to enhance the rich tonal qualities of the speakers, I'd try tubes with sufficient power. However, as I did not have any tube amps on hand at the time I owned the SFAAs, I don't have a specific recommendation. I would imagine that Lamm ML1.1s or M1.2Rs would be quite good. If you wish for a bit more drive, pace and bass control, I'd consider the Boulder 1060. I would also consider Spectral gear - however, you'd need to commit to a preamp-amp plus MIT cables setup. I would imagine that Spectral, which has transparency and dynamics galore (without sound bright at all) would nicely mesh with the timbre the SFAAs produce.
As Paladin mentions, Goldmund would also work well but are hard to find new or used in the US.
As Paladin mentions, Goldmund would also work well but are hard to find new or used in the US.