@recluse, my DSL download speed max is 6 megabits, and in practice is usually around 5.5 - sometimes less. So far, after about a month, I have not had any trouble streaming hi res files from Qobuz. I do occasionally have a problem streaming movies, caused by the unreliable service provided by my phone company (Frontier), and I expect they will eventually interrupt my Qobuz streaming too. But to answer your question, 5 megabits per second should be sufficient for hi res files.
New Qobuz User Comments
So, I bit the bullet and have Qobuz going for one month now. The Studio version, not the topmost tier. I cancelled Tidal because I wasn't happy with MQA sound and the relentless marketing of music I detest. I like Qobuz very much. The sound quality at all levels is outstanding IMO. My only gripe is I can't organize my favorite albums by artist and for now I'm stuck with "date added" listing when streaming through a Lumin T2. Qobuz says they are working on this. On my phone or laptop, using just the Qobuz app, I can display albums alphabetically by Artist. Via my phone, in the car, I have no dropout issues. When downloading Qobuz albums to my iPhone the download time is significantly faster than with Tidal. Finally, the Qobuz platform seems pretty stable and the music offered is sufficient.