BEST fullrange speaker drivers in existence, 4"-10" diameter range, and...Go!

Here you go
https://voxativnewsitedemo.squarespace.com/products/acxhb

And, are you asking for off the shelf drivers you can purchase separately from a finished speaker system?

ok, to clarify:

looking for the best midrange driver there is, for a DIY project that will include 2-4 of these per side.  I am specifically looking for a fullrange driver whose ~400-4000 Hz behaviour is reference standard. im testing some ideas about lower order crossovers and I have literally no idea what I am doing (yet)

effectively i must distinguish for myself whether or not, all other things being equal, that horns either are or are not decisively better (aka more "musical") than even the best speaker cone driver

I would check out the Pure Audio Project Horn 1 compression driver. I think its about 40 Hz to 20K. They also have the Voxativ versions (there are three, but VERY pricey).