I have never thought about subwoofers as resonant devices aside from port and box tuning. A resonant circuit is a significantly different thing to me. High moving mass does not necessarily lead to high efficiency; it is more dependent upon the volume of the box and any porting (there is resonance at the port, and a sealed box has a resonance point in conjunction with the driver parameters, but the vast majority of operation is not at the resonance frequency).
Bass extension and overall efficiency is a combination of driver and box parameters. And generally the problem with distortion occurs at higher levels, not the lowest signal, which requires less movement and thus reduces distortion. Drivers do not have crossover distortion so touted in amplifiers as causing problems at low audio levels (though that is largely a myth, not a subwoofer topic).
There are physical rules like Hoffman's Law limiting the efficiency one can obtain from a small driver such as you propose. And Helmholtz, T/S, and other formulas for designing speakers. Do you have any white papers or technical articles describing your approach?
