I'm not really following what the problem is. You can adjust the other speakers in relation to the mains and of course you adjust the overall level with the main volume control. Why would you undo the calibration by just changing the main speaker volume? As to not being able to calibrate at the 70dB range on the meter, are you sure that you didn't unintentionally set the -10dB setting on the mains in the set menu?

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Enjoy the music, not the equipment.