I think the reason for active is to couple drivers directly to the amplifier and get rid of crossover components. Also a passive radiator shares same compartment with the woofer and is coupled together by the air pressure, so I don't think two active woofers of different designs would work. The SS3 amp is designed specifically for bass reproduction with specific Thiele/Small parameters in mind and proprietary to the drivers.
Though nut to crack, but good luck!
