well what line do you want draw for you ?
power is power clipped or not.....
I would think if your speakers are spewing harmonic distortion from amp clipping you would have the sense to turn it down.... like wise if you are smacking the coils on the backplate and slamming the suspension from too much power you should have the sense to turn it down.... (If you begin to smell burning glue you should also have the sense to turn it down... lol)
BTW, Id hardy call your 'question' grammatically correct.