dm2010nox, The ANC in the Equinox is quite different from the one used in the Honda Accord. GM needed to only cancel noises in the 30-100 Hz range. Only the subwoofer can produce proper sounds in this range. The other speakers cannot effectively produce frequencies below 100 Hz enough to make a difference. So the affect of changing other speakers will not have an affect on the ANC in the Equinox. Changing the sub would, like you stated, possibly make a major difference. Thanks for the info you provided.
Just for understanding by others: Basically, while traveling at highway speeds, the I4 engine in the Equinox has a nasty side effect of a low droning sound. The sound is produced by the engine's tuning that changes the timing of spark plug firing and valve timing in order to produce very high MPG. The ANC was introduced to reduce this annoying drone. The ANC does not work (or at least was not intended) on any other sounds. The normal quiet ride in the Equinox is more due to good insulation and build quality.
I would think the easiest way to kill the ANC would be to disconnect the mics. dm2010nox, do you know where/what color these wires are? Or do you use another method?