Speakers most critical component, , now what fq's are most critical in speakers

So now that we have established that speakers are the vocal chords of a  system, thus making speakers the single most important component in any high fidelity system.
We need to open discussions of what fq's should we be ~most~ concerned about in deciding which speakers  offer the highest fidelity within this hz range?
Bass  20hz-30hz, Can we just let this go for a  moment, As there is really not much in classical within this range, Jazz you do have drum sets going on, its not all that much to be missed.
So really bass  begins to be critical at 40hz. 
High fq's, ,,,again is there really much happening in the highest registers in classical? Not really. jazz has snares and other percussion, but again, hardly much to make any dif if missed out in the say 12k+ hz registers.
I know Richard Gray did mention, although there might not seem to be much going on in the highest hz area, its the ~ambience~ which a  high quality tweeter brings into the recorded sound. I agree.

Now we  are left with the rest, the wide midrange area. Which represents 90%++ of our music.
lower mid-bass, starting at 50hz - 200hz
Low midrange 200hz-say 500hz
Mids 500hz-1khz
upper mids 1k-3k+++
These are rough figures
Point is,  should we be so concerned about the 20-40hz's, when basically only less than 1% of the recordings possess this fq range. 1%, who really cares if it is not ~there~.
Now for the highest fq's, well again, should we really be so concerned how high a  tweeter can voice? 

The one design that strikes me as fulfilling this super critical midrange voicing with fidelity and a  seamless wide band soundstage  is the design callled high sensitivty wide band driver, otherwise known as  ~The Full  Range~
There is no so called ~mid`tweeter~ that can match the performance of these same fq's when compared to a  high quality FR single source.
From the low mid bass all the way to highest upper mids, the FR just has a  much larger voice coil and cone area for dispersion. 
Mid tweeters are a failure, Including both Seas Flagships The Millenium and  The Cresendo.  When heard next to a  quality FR .
With this single source wide band driver, no additional tweeter is needed. 
Now in the low bass, say 30-80hz, it is recommended  adding some sort of  bass modual. 
Which will bring in another dimension making the bass floor, more richer and dynamic, eliminates a  sense of ~flatness~ about a  single source's voicing.
Now I've not heard the single source drivers from the 2 highest labs. My guess is both labs also will benifit from added bass configure.
So now we need to look at what bass configures voice the cleanest, low distortion, sublime and subtle.
For this task, I recommend you look at Seas Excel either the older Magnesium Cone or the newst Magnesium cone called Graphene, which are like 50% more cost, Not sure if its worth it. 
The ideal size will either be dual W18's, or a  single W22, maybe even a  W26.
This Magnesium cone material is so sublime in the 40-60hz's, that hardly any driver on the market will match it. With the copper phase plug. Not a  neodymium magnet, but still packs a gorgeous tight rich 40-60hz bass , and voicing the low mids with pure clean fidelity. Pricey but worth it. 
Capacitor for the Excel midwoofers should be Mundorf SilverGold Supreme of if you can afford it SESGO. 2X's the price of reg supreme. Superior vs their Aluminum model.

Compression tweet has no meat on the bones. Ribbons not beefy enough.
Seems a  high quality 6.5 FR is ideal for capturing a  true high fidelity complete  wide midrange fq band. 
With some type of bass configure beefing up the lowest end, 40hz-60hz. 
As i say I am not all concerned with the 20hz-40hz. 
There is just not enough music in the under 40hz to make me go further swaping out what i already have.
Now if you have no Seas Excel, I'd suugest go a  single Graphene W22 or a  W26 Excel Magnesium. 
I agree and disagree!  Big fan of seas excel.  Listening to some right now.  Also a big fan of bass.  My speakers play 25-26hz very strong.  I had a dip at 70 hz where bass was mia.  Dont underestimate the power of placement and room treatments.
I'm not sure if I follow. I may be looking at the wrong Seas drivers but the W18 or W22 are not full range drivers and at 88 dB I wouldn't categorize then as highly efficient. I thought you were talking about high efficiency full range single drivers - like what I have in my Omega Super Alnico Monitors. I think they sound fantastic for certain genres of music where upper bass through lower treble region is more dense than other regions. The high efficiency combined with the lack of a crossover gives single drivers a perceived sense of immediacy that is quite noticeable. 
Do yourself a favor and go listen to some Tannoys. I think that once you do, you will be hooked. That dual concentric driver is a beauty. I got the Eaton legacy and they are all I will ever need.