What amp are you using to drive the transducer? I'm wondering if there might be a way to pull something off there by splitting the Behringer's low outputs and sending a copy of the stereo low frequency signals to the transducer's amp in parallel with the signals to the two powered subs. If that worked and the transducer's amp had a trigger, you could even use the 950's zone trigger to power it on and off and then just turn on the second zone when you want the transducer going...