Dave, it looks like you certainly have gone through the archives. One possibility you haven't mentioned might be the simplest and best. Since your S10 has a xover input which bypasses the internal crossover and level controls on the sub, use it. Then the crossover(preferably at 80Hz)will be handled by your 945 and likewise the sub level, assuming that the 945 has an adequate range of sub level adjustment for the S10.

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Enjoy the music, not the equipment.