I had a 35 wpc Primaluna amp. Got the low watt bug and bought a Decware Mini Torii 4wpc amp. Kept my Ref 3A speakers ( rated at 92db eff.)
Other than not being able to bother the neighbors I got plenty of sound in a 12x20ft room open on the long sides.
Wouldn't mind a more efficient speaker but haven't seen one the trips my ticket.
Have a Grommes PHI-26 6 wpc speaker in a second system with 97db Klipsch Quartets both sound great just different