Funny enough, I can think of at least one site that bans A/B testing as a prerequisite for “proof.”
The thing is that everyone’s system and listening acuity is quite different.
On my system, things far less than the 1-4 you posted make an audible difference.
one is uncompressing flac files to WAV, which makes a larger difference sometimes than 44.1 vs. hires. But each jump to better files is audible. Even the drive I play the files off makes a small difference in sound quality (hardware Raid sounds better than software based raid).