I hear you Tom on the crossover point, I like the crossover bypass
switch, allowing the addition of a external crossover, really flexible!
When mine showed up, made sure they worked, then tore them down, 1gal of acousti x sound coat for both subs, 3 coats internally,
including the basket of the drivers, completely coated the amps with AVM, changed the fuses, eliminated the micro arcing with all of the internal mechanical connections, cones & shock pads, 75lbs of mass loading on the top of each sub, couple of decent power chords. Modifications were not expensive, transformed them into giant killers, total cost well under 2k thanks Underwood Hifi!