You do not want to go above 250Hz with the OB servo subs. That is why they are normally used with the BG NEO10's when they were available. The NEO8's need another driver below 800-1000Hz as in the LS-6 or LS-9 speakers.
Danny is working on a NEO10 replacement, but have not heard any updates. He maybe working with the GRS 10in planar as well.