Haven't heard the Belles or Sim amps, but have been able to audition the BC8s and Herron 150s with the Herron VTSP-1A, which I also own. First these are both great amps, and in the end the choice is really a matter of personal preferences.
To my ear the Blue Circle's are a bit more extended and detailed, the Herron's warmer and more organic. Both image very well with wide, deep soundstages. You didn't mention your speakers, mine are the Von Schweidert VR5-HSEs.
To my ear the Blue Circle's are a bit more extended and detailed, the Herron's warmer and more organic. Both image very well with wide, deep soundstages. You didn't mention your speakers, mine are the Von Schweidert VR5-HSEs.