roger, I suppose the answer to this question is that it depends. With program material without very much deep bass content below 25Hz, then maximum output mode will provide the highest output with lowest distortion. With other content, such as pipe organ music and some movies with very deep bass, extended bass mode would work the best.
Feel free to experiment with both modes. Just make sure not to run the subwoofer with both ports open and max extension mode set on the amplifier, as this could damage the subwoofer since there would be little protection below port tuning.
Sincerely,
