I have a whole setup of Monolithic equipment.
Two PA-1600 amps (2 x 100 watt)
Two PA-500 amps (2 x 50 watt)
Two EX0-2 crossovers
One ABF-1 amp fader
One EQ-4 preamp/EQ
When I was an installer in a car audio shop in the 80s we sold a lot of Monolithic. I bought all this to put in my car but never got around to it. It has all been packed away in storage. All the units are new and unused except for two of the amps, which were used briefly on the demo stand in our retail store. Half are still in the original boxes.
One of the x-overs I had the Mono guys customize the range at the factory to 300-1800 Hz.