I have never liked an efficient loudspeaker/set amp combo.
What is an efficient loudspeaker anyway? 100+db? 95+db? I’m not sure if I ever have had a speaker > 90db, but I have had some 85db stand mount speakers driven by 1000 watt monos that sounded fantastic, most of my speaker/amp combos were around 88db driven by 250-350 watt monoblocks