I have a pair of Klipschorns in my main system and a pair of 16 Ohms Zu Soul Superfly's in my secondary system.
Both pairs absolutely sing with a tiny 3.5W Miniwatt N3 amp.
The amp has 4,6 and 8 Ohm taps on the rear of the transformers but I have only ever used the 8 Ohms taps.