Designing a good crossover operating at speaker driver impedance is a mess.

From a system design standpoint we should not be attempting to design "flat" speakers and "flat" amplifiers, we should be designing a "flat" system and the "speaker" should accept a line level input, hopefully balanced.

Unfortunately, this will rob the audiophile of some historic choices. The drill has been to search for the "ultimate" amplifier, "ultimate" speaker, and "ultimate" speaker wire. It's a lot less fun if there is only one search. In reality, since the audiophile's room is what it is, a little DSP work inside the amplified speaker box could be helpful. (but probably not as helpful as some acoustic treatment) Unfortunately, DSP does not seem as "pure" as the ultimate amplifier.

A nasty practical detail is that a good speaker designer and a good amplifier designer are usually not the same person or company.