You might need a tube crossover, for your amplifier is really fast sounding, check "www.space-tech-lab.com" for different models, they made real good sounding tube equipments with one fraction of market price.
I have try a lot of bi-amp, tri-amp and quad-amp combination with different active crossover, but tube crossover is my final decision to go. The most important points is after crossover, the phase shift is different for different freq band, in order to compensate the phase shift, you should test all the +/- combination of all channel in order to get the best phase coherance. The best way to play around with a active crossover system is to build you own speaker set, each channel with different box, then you can adjust the different phase relationship by adjusting the relative position of different channels.
I have try a lot of bi-amp, tri-amp and quad-amp combination with different active crossover, but tube crossover is my final decision to go. The most important points is after crossover, the phase shift is different for different freq band, in order to compensate the phase shift, you should test all the +/- combination of all channel in order to get the best phase coherance. The best way to play around with a active crossover system is to build you own speaker set, each channel with different box, then you can adjust the different phase relationship by adjusting the relative position of different channels.