hi 9rw, you are correct, i8 offer no proof other than an opinion. thank you for your astute observation.
there is no proof as to perception of sound. its called perception because its not logic.
my purpose is to find out if anyone has perceived a change in frequency response when using the p 500 or p 1000.
it is possible that i perceive changes in frequency response which are not confirmed by others.
i accept that possibility.
ultimately, i may have to audition evry component i am considering for purchase and not rely on the experiences of others, because perceptions are idiosyncratic.