What's the best mid-range driver available?

ATC will not sell any drivers alone. There are only 2 distributors in the country and I know both. If you want to buy and demo pair, I can turn you on to the importer and distributor of ATC located here in Denver. Cheers.

yes, there is a place to get just the driver (sans magnet) it's based out of england.

The Skaaning or Flex Driver (other commercial name) used on the Verity is a thing of beauty. Fast as lighting with the best midbass I have heard. My two cents.

Yes the Skaanings are very nice. The Danish DIYer , Mogens Anderson has a 3 way Skaaning + ATC + Scan-Speak. He had Skaan build a 5 inch with specs of his choice. The only thing he would change is the tweet to a Hiqulaphon. Take a look. http://home13.inet.tele.dk/meil/

I believe Solen in Canada sells ATC (www.solen.ca) just for reference. What I don't get with the R-3's though, is I could swear I've seen design/kits using and R-3, but then crossed to an R-2 or R-1 to finish on up to 20khz ?????(Big Time)????? Unless there's some reflections of the wavelengths in the upper registers given/relative the dimensions of the R-3 that actually warrant one of the smaller Ravens better at the high-frequency extremes and the crossover worth it--I can't think of any reason to do something like that. But can't the R-3 be crossed even lower than the ATC dome-like 500hz with the R-3. If it were to be an active system-the money saved on xover parts and an extra set of amps would be a strong point in favor of a two way R-3 setup.