Not true...
The sonic performance output of an amplifier is
How well the amplifier's output stage matches the demands put on it by the loudspeaker load. The biggest component variable in the signal chain is the loudspeaker..
This depends on the electrical design of the loudspeaker, choice of drivers, driver materials and x-over design.
For example, 1 loudspeaker like a Klipsch RF7 (8 ohms, 100 dB sensitivity) is EZ to drive due to its high sensitivity, higher impedance and horn tweeter. But take a Revel product such as the Salon 2 (4 ohms, 86 dB sensitivity) with its inverted dome tweeter, its complex x-over puts heavier demands on the amplifier's output stage and power supply.
If an amplifier is driving the Klipsch loudspeaker its power demands are much easier to handle than the Revel so quite likely fewer negative audio byproducts will be audible... Therefore the load and driver & x-over specs of the loudspeaker on the amplifier's output stage is
what separates the sonic performance from 1 amplifier to another. The easier the loudspeaker load is to the amplifier is, the
more similar the sound of between the comparable set up amplifiers will be. When a loudspeaker/load is too complex for the amplifier to handle this is when this is when significant negative byproducts become audible. Thats why when in investing significant $ into an elaborate audio, it is pertinent to confirm the amplifier is capable of driving the target loudspeaker.
Note that when selecting an amplifier, crucial specs such as its topology, headroom, slew rate, IM distortion, power supply reserve are very important.. To dig into these deeper, we should start another thread.
Just my $0.02..