It's going to be hard to shplain the things we hear now once the aural adjustment hypothesis takes hold. Everything will hinge on exactly what you said regarding brain adjusting. And for all I know that just might be the case after all; hard to believe though. I notice a difference with the oils in coupling caps and that seems to be a nice change from the drops. But then I find if I like the amps sound then I like all the caps in it; just different sounds. The oils sometimes seem to be more spacious. I mean I know there is a difference I just don't know for sure if something is better in a particular circuit.