I have made direct comparisons between red book CD, the same Qobuz recording, files located locally… exact same sound quality… however Qobuz is frequently better because the have 1/2 million high Rez albums. My DAC is my CD player… and my preamp allows volume leveling between sources.
Having said that… the streamer and DAC make the biggest difference in the sound you get. My system is very good, so I can hear subtitle differences in sources. But of course if you are not changing your equipment, tyou are going to get the best sound from Qobuz.