Question: Does ATC have the best midrange driver?

The ATC mid is fantastic. no doubt about it.

what makes it sound so well is the fact that ATC crosses at 380/3500 Hz in all their models, meaning that the vast majority of musical information comes through a single, high quality driver.

What is most important is that for many years ATC's SM75-150 midrange driver was considered the best and it was ahead of its time. There are many good midrange drivers nowadays, but the fact that ProAc chose it for its expensive Carbon series says a lot. Being a dome is one of the reasons, as Audiokinesis explained so well.

They are not even Close to the best but they are common and very good!