The watts that it takes to move a motor is in the same overall range that the same motor will generate when moved. So, if you use a power amp to drive a speaker, you should treat the power a speaker generates as being in the same range. So the question is would you plug the output of a power amp into the input of a microphone preamplifier? I hope not.
For a more precise answer you should ask the geek slutz forum here and I am certain someone will know exactly the risks - but I would assume you could fry an op amp with that sort of current .. and no one would provide warranty service... i think it would qualify as abuse.
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