For classical music fans looking for the best sounding classical internet radio stations, the amount of compression the station applies is very important. Many times the amount of compression a given station is applying makes all the difference, far more difference than the actual bit rate of the stream. You can recognize the really "high fidelity" stations by how quiet they sound compared to most others. You want the least compression and therefore the "quietest" stations.
Most recordings, even classical music recordings, have considerable compression applied to the signal during the recording process. To hear the most lifelike sound, you certainly don't want the station applying a lot of additional compression. However, in my experience, one of the ways most internet radio stations, even those specializing in classical music, process their signal is to add extra compression. This is immediately obvious when comparing the sound of a particular recording playing on an internet radio station with the CD version of that program played from Qobuz or Tidal.
Here are a few classical stations I've found to have exceptional sound quality in terms of lack of compression. The sound quality of these stations is exceptional as internet radio stations go despite the fact that none of these send out a signal at a bit rate of more than 128 kbps:
1. New York's WQXR has a very nice-sounding signal, and plays a wide musical variety, not concentrating too much on classical "war horses." It is one of the very "quietest" signals out there in internet radio land. That means it is uncompressed. It would sound even better if they boosted the resolution up from MP-3 128 kbps.
2. The two Australian Broadcasting Company (ABC) classical stations Classic and Classic 2. The ABC Jazz channel shares this low compression/quality sound characteristic. Unfortunately, the bitrate of all three is down around 64 kbps. They still sound quite nice, considering.
3. BBC Radio 3 (AirPlay from the BBC Sounds app is the best-sounding BBC Radio 3 stream available outside Britain)
4. WILL (an NPR station out of Champaign/Urbana Illinois, home of my undergrad Alma Mater, University of Illinois). When playing NPR material, it's frequently shocking how much quieter and better WILL sounds than the same program being simulcast on other NPR internet radio stations. The average SPL difference frequently exceeds 15 dB.