You are correct that having two crossovers at such a close frequency can lead to integration problems. It's not ideal. That is why I say to use a lower crossover frequency for the sub, or to use the speakers full-range along with the subs, although that does take some work to get right.
If you plan on crossing over the bass to the subs, just make it easy on yourself and get the 1723 S Monitors (or regular 1723 monitors).