Dermott, Peter may be off the board for the evening, but in my view the point should be that neither is "better sounding"; they'll both amplify transparently when operated within their designed limits and won't introduce any "sound" of their own.
So far as the auto-calibration, in my view that's an advantage especially if someone isn't inclined to do a manual calibration with a separate meter. That'll give them a better effect than if they left things totally alone. Hopefully they'd be willing to at least use the microphone for the calibration. So, get them the 657.
