It sounds like you are looking for a 2-channel bass management controller with a high crossover point. The devices are typically active and allow biamping with powered subwoofers. The two that I use are both from M&K and are set at 80Hz. Hsu Research has a model that allows some flexibility in the xover point, but probably not as high as you wish to go. Of course, any active stereo 2-way crossover (Rane, for example) would work.