The motor in the Extremis is not very strong so the sensitivity is low. I also found the Qes to be too high for a properly damped ported box. A sealed enclosure performed well but you would still need to add a subwoofer. At that point the other drivers available perform better (smoother frequency response, higher sensitivity)and in the case of the RS180 it's much lower in cost. It doesn't make much sense to have the extra excursion capability if you're not going to use it anyway.I think the best Extremis application would be a small sealed subwoofer with added equalization.