I have absolutely no experience with subwoofers, neither in the car nor at home. But I could imagine that there's another plus point if you can lower the crossover frequency to 100 Hz. I suppose, but I could be wrong here, that the pitch is more clearly identifiable from the focal in the upper bass range than from the subwoofer. Some subwoofers tend to have an - albeit strong - foundation, but a bit of a one-note bass effect. If the Focal runs down to 100 Hz, then this is the octave from the low G on the double bass, although not the low E, but still. This way the Focal as an overtone from the low bass notes can improve the identification of even those bass notes that it doesn't transmit itself.
