Congratulations on the Harbeth SHL5 Plus speakers. They are very natural sounding speakers and will sound great with almost all genres of music. I haven’t listened to the Pass Int-150 or Bryston B135-SST2. Some of the natural partners or good amp combination for the Harbeth are the LFD, Croft, Sonneteer and Naim amps. Mostly British. Having said that, the SHL5+ will sound equally great with any amplifier, spectacular with select amplifiers depending on your room, listening preference and partnering equipment.
Enjoy.
Enjoy.