The midrange is the most important driver.

Totally agree.

For high fidelity the order for greatest importance in a speaker

1) Mid range (300 to 3KHz)
2) Bass (40 to 400)
3) Tweeter (2KHz to 20KHz)

For BS hype Speaker marketing it is ALWAYS the tweeter that is emphasized most. This is entirely because a tweeter is the simplest and cheapest part in a speaker and easily upgraded or replaced. So spending huge extra amounts on a tweeter costs the maunfacturer the least $ for the maximum in marketing hype!

Sadly customers fall for this marketing trick all the time.

Worse than sad. Many of the fanciest Berylium unobtainium diamond tweeters contain cheap ferrofluid so that it is really CHEAP to make the tweeter, as the tooling and engineering precision can be really sloppy because the cheap ferrofluid just band aids everything!!! So within as little as two years this fluid has dried out and your super duper tweeter sounds dull and it is time to upgrade again!

Given that by far most of the musical content is in the 300Hz-3KHz frequency range, one could surmise that the quality of driver which covers that range plays the most significant role in the ultimate sound quality that is heard, assuming all else being equal. In my experience with multi-way speakers, I think how the sound transitions from one driver to the other is equally if not more important than each driver by itself.This discussion poses an interesting question of how this all applies to planar or ESL designs.

@kalali   Exactly!!  As a long time and current Vandersteen owner, you will scarcely hear a man as passionate about that very issue as Richard Vandersteen is.  All of his speakers have employed first order crossovers as he finds that strategy the best way to make speakers with a variety of drivers sound "of a piece".  That's what Vandersteen's catch phrase "Dimensional Purity" is all about.

I learned to listen on my original Quad ESLs, which I bought in 1973. They have a peerless midrange that, even 60 years after their introduction, is still considered a reference or benchmark. Living with them as a full range speaker poses a number of challanges-- very beamy high frequencies, requiring an almost head in vise listening position- an inability to play at stadium power levels (which I rarely do) and a roll off in the bass that is difficult to rectify by adding subwoofers. (Adjustment of the speaker within the room, changing their height and tilt can affect this).
To me, the first "tell" of a system that has artifacts is the midrange- if it sounds boxed in, or grainy (which may have as much to do with the amplification as the speaker), I’m pretty much out. I can tolerate sins of omission or other limitations such as those presented by the old Quad better than a compromised midrange. When I upgraded in around 1990 to a pair of Crosby Quads, I found that speaker to do everything better- it played louder, had more bass, the high frequencies weren’t as beamy, but it didn’t have quite the magic, the utter transparency, the spooky realism that the original Quad ESL did.
I switched to a horn-centric system in around 2006-7. One of the vital aspects of the horn (Avantgarde Duo, which is polarizing speaker- people seem to love or hate ’em, which is another subject) was its transparent midrange, which was, for me, brought to life with the Lamm ML 2 SET. The horn presents a different set of challenges- totally unforgiving of upstream components and there is a fine line in getting the bass right (short of having Jim Smith come to your home).

I have heard dynamic speakers that are, combined with the right electronics, also convincing in the mids, so I’m not advocating one type of speaker over the other, but there is still something unbeatable about those old Quads. I have, as mentioned elsewhere here, had my old pair restored, and they are set up in a vintage system in another room. I love them despite their limitations, and they sound even better to my ears today than when I had them as college student.