Most coherent low volume speaker with very fast bass under 10k used?

For 70db & medium sized room
+ matching amp recommendation please
((Most coherent low volume speaker with very fast bass under 10k used?))

Vandersteen Quatros
Adjustable bass = clear in room bass response.High Pass allows the amp from heavy lifting = dramatically lowers distortion further improving transparency and clarity at all volumes.

I would like too add that I like wide dispersion speakers. Think ATC SCM50, with the coherence and speed of a quad 57, and dynamics of horns.
Low volume listening isn't necessarily compatible with higher level listening as a design conundrum exists…Fletcher Munson et al...powered subs ("fast" bass is a term I find meaningless) can help if low level listening is what you want…you can turn the relative level up…who knew? Horns at low level better be pointed at your head, but I still think any speaker that somehow exceeds at boosting the frequencies that otherwise drop off at low levels can over boost those frequencies when you turn stuff up. Get an equalizer maybe as at low levels you don't get proper musicality anyway, so who cares if it adds crap? 
Well, i mention very fast Bass because this is the weak spot of all speakers. High inertia of the large bass driver or time smear with multiple small ones destroy coherence and introduce timing problems. 85db - where all frequencies start to appear even - is far too loud. I think there is also a market for excellent low level speakers that are optimized for 70-75db. If you play that speaker louder and bass and highs get too intense so you turn the level down again - well that can only be a good thing for our ears.