Yeah well just buy externally powered subs and never have to worry or complain about it.
That will work for ported subs, but not sealed ones or servo subs like the OPs. Sealed subs need Eq below F3, and then a high pass filter to stop driver over excursion. Basically that is what I do, although my long main lines are a sub plus and each requires two power amps as the two drivers do not receive the same signal.
I do understand the convenience of a sub plus amp. It reduces clutter, and also allows for phasing and volume trim and issues like that.