yes, you have to listen to different subwoofers to appreciate if there IS or ISN'T an audible difference. I would recommend that you do the same ... i'm not actually pulling things out my ...
and you are talking about overall SPL when it comes to speaker sensitivity, with subs, we talk about how specific frequencies require MORE watts than another higher frequency at the same SPL. the lower you go, the more power you need.
you'd be surprised how much better it is to have headroom you say you don't need.
and how big of a difference there is between the axiom and the other subs in that pic.