The 'biamping" arrangements on speakers I've looked at appear to only split the passive crossover into two sections that can then be powered by separate amps. This probably helps some by isolating interactions between the low-pass and high-pass sections, but real gains in performance come from eliminating the passive crossover altogether and using an active crossover with multiple amps. So far as I can tell, that would require getting inside the speaker cabinet and disconnecting the passive crossover, or at least the section that is going to be replaced by an active crossover (in case of more than two-way), and wiring the back panel jacks straight to the drivers. Otherwise, using an active crossover will put the active in series with the passive crossover in the speaker cabinet which gains nothing. With passive crossovers, the lower the frequency of the crossover, the bigger the inductors, and big inductors create all sorts of sound quality issues. It's a credit to passive crossover designers that they get them to work satisfactorily at all.