Primephonic is the only music streaming service I have seen that offers just classical music to stream. Classical listeners are often the most sensitive to hearing and therefore need to be offered top quality audio files.
Primephonic answers this by having two different options. One plan with 320kbps MP3 (the most you need for listening on a mobile app) and another Platinum service at an impressive 24-bit lossless quality for higher end music devices/setups. The free trial is for 14 days.