You can also make a more efficient speaker by "tightening up the tolerances" (i.e., tighter fitting voice coil/gap) and increasing the number of windings within the same area (e.g., using flat-wound wire), without causing other problems.
BTW, a lighter cone will also allow the driver to play to a higher frequency without break-up.
My "Merman" speakers are extremely efficient, and sensitive, without horns, and can easily do "live concert levels" and I wouldn’t have it any other way.
Remember that the volume control is nothing more than a "focus knob" and sometimes you really need that volume to bring the cut into focus.
Also, I feel that an "immersive experience" takes realistic volumes to achieve. You can't immerse yourself in a tub of water if it only covers your toes.