These are your equipment and you should set it up the way it suits your needs.
I followed the recommended setting (small with xover at 80 hz and 0 db on the receiver and 150 hz on the sub) because I did not want to strain my receiver and front speakers playing lower frequencies. I like the sound both in stereo mode and movies. In the evening if the sub tends to be too loud, I just reduce the volume. Although M80's can be set to large, the 12" sub is better equipt to handle this task than the 6.5" drivers of the M80's.
This way I also avoid the need to shift from large to small and vice versa when I play music or watch movies.
I compare it with hauling 200 lbs of bricks. I can use my car and it will definitely work but my pick up truck is better equipt to handle the task. Of course there could be other reasons why I might still want to use my car.
