Eldartford is correct; driving the speakers from any tap will damage neither the amp nor the speakers. The voltage delivered to the speakers (and the sound-output level) will increase with each step up the impedance taps, but the amp still won't deliver more than the same amount of power.
So you'll get more volume up to a point, which seems to be what you want, but listen carefully--the system will sound different from each tap.
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So you'll get more volume up to a point, which seems to be what you want, but listen carefully--the system will sound different from each tap.
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