Adjusting the filter between sub and speakers can make small differences and improve the match. Most DSP amps will allow you to do this. (Filter slopes are typically between 24 db/octave and 12 db/octave.)
However, adding a capacitor in order to minimize the signal path does not seem like a justifiable reason for making this kind of adjustment.
However, adding a capacitor in order to minimize the signal path does not seem like a justifiable reason for making this kind of adjustment.