Hi efficient speaker, bass problems

Boy T M please rewrite your post. Efficency and sensitivity are not the same but not different only opposite. Thus bass is not opposit only different ? ? ?

In that case it is prolly a function of amp output impedance and not
power. Tube amps, especially set amps are of high out put
impedance. When this reacts with a speakers impedance which can be low in the bass and higher in the treble (without a zobel network which
wil lower efficency) the result is a less controlled and responsive
bass.

Extension, dampning and efficiency are the tradeoffs. The vectors go in different directions. The op questions grip vs eff. The extension is not. as I understand. part of the query. But I'm all in for a free lunch of any kind. Elucidate