Ok... curiosity has me and I have to ask. I've tried to watch the build videos as much as work allows me to, so if I've missed this, I apologize for the redundancy.
But. Are those "old style" choke/coil crossovers? I admit I've been "out" of the audio game for a long time, but I love good builds. Those look much like the ones I use to get from Radio Shack back in the day for a my cheap second hand third rate junk that I filled my beat up cars with. Granted, it was all I could afford, it played well and sounded ok for the day.
Seemed to me that you just about can't find those things anywhere these days except by very specific suppliers because of the variable electronic external/internal crossovers. I've never had my hands on one, but I'm pretty sure if you cracked open a crossover that comes with most component sets, it would be the same thing inside them as was in the late 80's. Thats just a very modern and attractive setup.