I have tried mine with amplifiers from 12-300W. Negligible difference. If I give them more than 1 watt they sound odd, even unpleasant depending on source material.
Sure. With one watts these guys are pretty much over the cliff. Reiterated, distortion matters. If a speaker has a severe peak, say 1% or even below, but acummulating all the harmonics at the same peak, that actually is perceptible as: "ouch!". The hearing would take the information as an alert. That it is highly unmusical is taken for granted.
I cannot imagine to drive a speaker even farther to equalize, sorts of, the distortion profile?! Nobody would do that.
On the other hand, who would actually expect real high fidelity from this product, I mean with some substance in the physical presentation, impact? A lifestyle accustomed to share the latest pop song on the eye-phone with all the gals in the office, doesn't need more. Normal speech is about 60..70dB, only to give a reference. I ask for more from my 4 x 12inch midwoofers plus, ehm, horn. But rarely.
Anecdote 7: Just today I got an 18sound 12NDA520 repaired. It had, at levels way beyond 90dB some sisseling, wheezing. Very very low in level--about minus 50dB or so. The spectrum was contaminated up to a high 10kHz, though. It was abandoned for years. Reason was: an intermediate glue point for the leads at the spider was a little loose. At 554Hz the spider gets into resonance and the miniscule rattle copies through the paper cone to the outside. Nasty ... it spoiled all the fun with these overengineered oddballs.