I use three speakers with horn loaded upper ranges. Altec 19, JBL Apollo and Klipsch Cornwall. The Cornwalls are 100db sensitive, meaning that they will play at 100db with one watt input. So yes, they run easily in my big room with less than 5 watts. In fact they will run you out of that room with a 71A amp that outputs around a half watt.
But that gets to the other part of the equation. Large horn speakers need large rooms IMHO to sound good. Smaller horn speakers are better for small rooms.
There may be better setups for likelike presentation, depending on your definition of lifelike. Big electrostats and some mult-driver speakers can sound very lifelike, but without the jump factor of horns. Even some minis, like the KEF LS50 can get you there, but everything is scaled down a bit for a smaller room.
But that gets to the other part of the equation. Large horn speakers need large rooms IMHO to sound good. Smaller horn speakers are better for small rooms.
There may be better setups for likelike presentation, depending on your definition of lifelike. Big electrostats and some mult-driver speakers can sound very lifelike, but without the jump factor of horns. Even some minis, like the KEF LS50 can get you there, but everything is scaled down a bit for a smaller room.