Single driver loudspeakers

I know some friends who have built single driver horn loudspeakers with 6-7 inch 'full range' drive element and seem very happy with the sound.  However I wonder about those selling 94 db sensitive 12 and 15 inch full range drive elements and recommending 2-3 cubic ft bass reflex cabinets and 7 watt SET amplifiers.  Is it possible for a 15" 'full range" driver driven by 7 watt SET  to provide state of the art sound without audible distortion, deficient frequency extremes and 1950 style sound?  This is an inquiry not a critique.  Thank you for helping me to understand full range drive units.