We have this problem with saxophones (and even the type of finish), mouthpieces, trumpets, guitars, you name it. Very subtle differences may be heard. Or imagined.
Many can hear a difference between sound A and sound B, but does that mean that A is better than B? Not necessarily.
I did one little series of blind tests with mouthpieces and saxophones. Invariably the listeners preferred the brighter tone, that is, the setup that had more treble or brilliance to the sound.
If you do A/B testing with amps, speakers, whatever, listeners will prefer the one that is louder or the one with more bass... whether it is more accurate or not.
One thing you must not do is listen to synthesized music, electronic instruments. There is no reference to what is the intended sound. Listen to acoustic instruments for realism. And even here, how they are recorded makes a huge difference. Are the instruments recorded each in isolation and later mixed as psuedo stereo? Or are they recorded in an actual room, in stereo? Live orchestra on stage, a jazz combo, etc, will give a better indication of the capabilities of an amp/speaker setup.
