Ah, you did not explain what you were trying to accomplish. The Meridian G68 is a HT processor just like the Marantz 7701. However, the G68 also has digital outputs with communication outputs. Generally, digital outputs are full volume signals of the waveforms, so I am assuming that Meridian uses the comunications connections to have the Meridian active speaker control the volume by adjusting the amplifier gain. This is all prioprietary from Meridian.
If you are tri-ampliying your speakers and want to improve over your Mini-DSP, I would look at high end active "pure analog" crossovers. Here are a few:
Marchand Electronics (several models and configurations, include a tube crossover)