You won't be able to tell the difference between a really well encoded MP3 and the same song as FLAC. Not on the equipment you list, unless it's doing something to alter/color one of the tests. It doesn't really matter if it's in a car, on a bus, on a plane or on a train. Or in a home or in a studio. With Dr. Seuss or with a moose. Unless you or the people you're demoing for have some super golden ear... And a large percentage of those claiming they do are either lying or delusional.

It might be easier for some people to do a straight lossless FLAC encode than to set options to get a nice MP3. But if your rip introduced the noise, it doesn't matter what you encode with anyway.

But anyone using tubes for amplification obviously doesn't care about reproducing the true sound of the recording.

Bruno