My take..
While good intentioned, this article only convolutes this topic and further confuses sparsely and misinformed consumers.
It's quite obvious 5.1 configurations are the still the industry standard, proof of this is bulk of the currently mixed soundtracks offered on DVD format. While this configuration is quite adequate in many listening environments and applications, there are benefits to the use of 6.1 or 7.1 configurations.
As our listening capacity is more capable as well as critical 180 degrees in front of the listening position, the currently used three front channel configuration adequately provides a full sound field. Evidence of this is found in the amount of information provided in these channels on most soundtracks as well as the emphasis of the loudspeaker's capabilities to smoothly pan from left to center to right. It's possible to provide additional channels ( e.g., far left, far right, left center, middle center and right center), but due to the ability of the accuracy to pinpoint sound in the forward 180 degrees, the further addition of channels or speakers would likely provide diminishing returns.
In a larger listening environment (approx. 2,500 cubic feet or larger) where ample space is available behind the general listening area, a 6.1 configuration provides a more enveloping sound field as opposed to a 5.1 speaker configuration simply due to the fact that the additional channel, while it's signal is still matrixed from the surround signals (on 5.1 soundtracks, 6.1 discrete soundtracks are available in limited release), can "fill in" the area that the side surround setup falls a bit short on. One way to possibly fill this void in a 5.1 setup is to use dipole/bipole type speakers which diffuse the surround signal and provide a broader sound field for the listening audience. This still, however, generally does not produce the more encompassing, spatial sound field a 6.1 configuration is capable of providing.
In addition to the more enveloping sound field the 6.1 setup can provide in comparison to a 5.1 configuration, the 7.1 configuration, in which the two rear surround speakers will split the matrixed surround signal, will produce an even broader sound field as sounds produced behind the listening environment can be distinguished much easier when not located directly behind the listener. It doesn't take a scientist to realize our hearing capacity is more prominent in front of us than behind is. Regardless as to whether the soundtrack was recorded in 5.1, 6.1 or 7.1 discrete channels, the additional rear channels help fill in any gaps in the listening area.
Although very few soundtracks have been mixed with 6.1 discrete channels and none (to my knowledge and that are generally available) have been mixed for 7.1, these additional channels or configurations can be quite beneficial depending upon your application or listening environment. Most of this is subjective, but then again, so is a large portion of any auditory comparisons. While the necessity of 6.1 or 7.1 is irrelevant, as surround sound in general isn't quite a "necessity", these options provide just that, more options for the consumer. The best thing to do is be an informed consumer, for this topic, or any other for that matter. By the way, since when is having options such a bad thing?
One last note, overdrving your receiver and speaker sensitivity (often confused for efficency) has very little to do with the 5.1 or 7.1 dilemma...
