What about doing it all digitally? Data to the speaker, 1 DAC per driver. Model the ideal crossover in software/ implement in a DSP prior to the DAC, feed the DAC output direct to an amp optimized for the particular driver. No phase issues, an you can even add delay to time align the drivers.
What's that you say? Prior Art? http://www.meridian-audio.com/media/14218/dsp8000-ds2.pdf.
It'll never catch on, where are the endless tweaks, and the swapping of components in the hunt for Synergy