Generally speaking, 80Hz is a good starting point. You can experiment with different ones to find out which works best.

I would use the crossover in the receiver and bypass the sub's. It sounds like you have it right.

The same amount of power is going to your speakers, large or small, it's just that there is more power reserved for the "big bang" stuff. (I think I have that right)

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"Nothin' up my sleeve. . ." --Bullwinkle J. Moose