EPDR more important than impedance alone

Why not?
Quantum sez if you measure something you change it.

Good stuff

Buyers of expensive speakers need to "try" to understand the EPDR loading of them if they want to know if there amp/s are up to the task of driving them properly and getting the best out of the them.
https://ibb.co/SDSxxBB
https://ibb.co/qnwNwyF (the purple calculated epdr trace is the important one)

Cheers George

their (not there) 

EPDR- just what OCD audiophools need. More acronyms to worry about.

A steep phase angle can make a speaker difficult to drive.
Low impedance can make a speaker difficult to drive.
Neither phase angle nor impedance are steady over the frequency range of the speaker.
Phase angle and impedance are not tied to each other--they vary independently.
If one wants to get a better snapshot of just how hard (or easy) a speaker will be to drive, it seems to me to make sense to look at the big picture (aka EPDR) rather than a smaller one (the traditional impedance spec).

EPDR- just what OCD audiophools need. More acronyms to worry about.

Only if your not interested in trying to understand what your amp is capable of doing with what speaker.
Then you get on the amplifier/speaker merry go round with your
https://i.dailymail.co.uk/i/pix/scaled/2013/12/18/article-0-1A2B262D00000578-818_636x382.jpg

 it seems to me to make sense to look at the big picture (aka EPDR) rather than a smaller one (the traditional impedance spec).

Yes very true, traditional impedance specs only give half the "load" story.

Nasty combined impedance and - phase angle (EPDR) loadings nearly always seem to happen in the bass where most current is needed from an amp, and that's where many amps fall down, even "if" they have huge 8 or 4ohm wattage spec, they fail miserably into these EPDR loadings.

Cheers George

In general though, if your amp produces twice the power into 4 Ohms as it does in 8 Ohms, you should be in good shape for an 8 Ohm rated speaker.  That will give you plenty of current overhead, regardless of the phase angle.  Do note most amplifiers can't do this but do come close.