Geoff, if you set the mains to "large", then by definition they'll be playing their full audio range and the crossover, 60Hz or whatever, will have no relevance to them, but just to the speakers set "small". 60Hz is too low for your other speakers, so leave the crossover at 80Hz, even if you want to try things with the mains set "large".

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Enjoy the music, not the equipment.