first of all, you need at least a 3 way active crossover with the front channels set for highpass and the rear channels set for bandpass and of course the sub set for lowpass. The most common crossovers don't have this bandpass function on the rear channels.
then you need at least 5 channels of amplification. 2 for the tweets, 2 for the mids, and 1 for the sub.
that is the minimum requirement.
it is my understanding that it is harder to tune a fully active system, meaning you will need one of those fancy equalizers.