The crossover in this case is mechanical, in that the normal rolloff of the drivers themselves provides the crossover. I've used both the tweeters and the midwoofers in each of these designs with crossovers when they've been incorporated in other systems. But in this case, you'll not gain anything. The midwoofer and tweeter are paired nicely, just the way they are and with no need for additional crossover components.

So I think you'll want to continue to focus on the preamps, amps and connections for the solution to this problem.