For the theory is like you mentioned above
I can not explaned more what you wrote above
In My experiance i have noticed the SQ different that so Far Toshiba Exceria is My best micro SD Card
I Had compared to San disk , kingstone and Other brand
Please try The Toshiba Exceria and compare With Your existing now .
My goal hear on head fi that For new bie can direct buy the Good ones
There never was a theory, the fact is an SDCard is just an exact storage device. What you store in the card is exactly what you get. The only real difference is the write/read speed between 2 cards which does not matter for music playback.
You can always hear a difference when you choose to. This one will easily fail a blind AB testing.