Tim—With respect to the use of subwoofers to reduce room-related resonances, hey, the more, the better! Of course, most listeners have constraints that prevent adding more than two subwoofers to a modest-sized listening room. Certainly two is my limit, and I suspect that two subs is as much as most people would tolerate.
Regarding location: Assuming a front wall position (that's the normal personal preference), and given that such subs should be OUTSIDE the main speakers, a 16 ft. wide listening room (such as mine, also yours) would then dictate that the subs be in the corners—or virtually so. In that event, some toe-in would likely be helpful. In practice, decor-dictated personal concerns will probably determine where the two subs must go, and that's generally in the corners too, as they're likely be the only open area.
The "distributed array" concept is worthy with one notable exception: It generally (?) recommends leaving the main speakers UNfiltered. While that can be beneficial with respect to reducing low frequency room mode response, it ignores the primary benefit implicit when using an active electronic crossover to separate the ultra-low (<100Hz) bass passband (subwoofers) from the low-&-mid bass passband (main speakers). That separation assures that the main speakers (and their power amplifier) no longer have to process any heavy low bass energy. Those low bass frequencies now get shunted to the self-powered subs. That's an important advantage, and it's way too vital to bypass.
Regarding location: Assuming a front wall position (that's the normal personal preference), and given that such subs should be OUTSIDE the main speakers, a 16 ft. wide listening room (such as mine, also yours) would then dictate that the subs be in the corners—or virtually so. In that event, some toe-in would likely be helpful. In practice, decor-dictated personal concerns will probably determine where the two subs must go, and that's generally in the corners too, as they're likely be the only open area.
The "distributed array" concept is worthy with one notable exception: It generally (?) recommends leaving the main speakers UNfiltered. While that can be beneficial with respect to reducing low frequency room mode response, it ignores the primary benefit implicit when using an active electronic crossover to separate the ultra-low (<100Hz) bass passband (subwoofers) from the low-&-mid bass passband (main speakers). That separation assures that the main speakers (and their power amplifier) no longer have to process any heavy low bass energy. Those low bass frequencies now get shunted to the self-powered subs. That's an important advantage, and it's way too vital to bypass.