Elden, unless you're planning to use a separate external crossover before the amplifiers(and entirely separate amplifiers)and remove or bypass the M80 crossovers, nothing significant would be accomplished. On the impedance question, the separate low and high frequency sections of a speaker have the same impedance and, as Rick commented, passive biamping doesn't change this.
No, Axiom doesn't have bi-amped graphs available, and Alan has made clear that the process isn't considered to be worthwhile. The presence of two sets of input terminals is essentially a concession to marketing considerations rather than reflecting principles of audio technology.
