Is there advantage in more watts, uneed?

The more you demand from an amp the more noise you get.  Plus if you "run" at the rated output, a transient is more likely to put you into clipping and that also sounds bad.  Yes it can be bad.

Been through this topic once or twice before.

I too am a believer in "headroom", but as stated by DYohn, correct setup is critical.

Also note that theoretically it takes twice the power (or number of speakers) to produce a 3decibel gain in audible output. A gain of 10db is noted to be "twice as loud". You would need to go from a 100watt amp to a 200watt amp to see a 3db gain, of course there would be no point if the woofer could not handle the power thermally or mechanically.

For the sake of discussion, if you wanted the sub to produce twice the output, it would take going from a 100watt amp to almost 1000watts. Not to say you couldn't use a 100 watt amp on a sub rated for 1000w, but simply to make the point. However, put 1000watts to the 100watt sub, and most likely you will experience damage in a fairly short time. So IMO, the difference you will notice betwen a 100w amp, and a 125 watt amp, will be slight, if any, all else being equal and setup properly.