Active CrossOver for Biamping Maggie 2.1's

I have a set of 20.1's on order and plan to bi-amp them using an active crossover. I am thinking about getting the Bryston 10B Sub for this purpose which I understand has been recommended by Magnepan and is an audiophile grade component. I would appreciate it if someone could advise me of the crossover points and slopes for the 20.1's. Also, I would be very interested to hear of anyone's personal experience with the 10B Sub or any other active crossovers.

Other components in my system are Aragon Pallidum II amps, Aragon 8008BB amp, BAT VK-50SE preamp and VK-D5SE CD.