Pretty sure the TL;DR is, in theory anyway; the more dedicated the circuit, components, layout and materials, the less you “change” the signal as you move through the chain.
IE – top end amplifiers – hand built and tuned, dedicated audio componants. Budget amp, off the shelf ICs and no individual adjustment etc etc.
The jokers in the pack are source quality, law of diminishing returns, and the fact that some distortion can “improve” the sound [see valves and valve-heads].
Then there’s the bullshit and placebo, as above.