Let's try to get back on-topic...
Consider the following image:
(Click the image to see a larger, higher-rez version)
This image was posted by Audionut11 in this thread.
It's a screen-cap from the movie The Matrix.
Examine it closely because it has implications across all the discussions in this thread. The 3rd trace is the CC, (cyan.) If you examine it closely, it is very clear that the CC is the strongest channel with the strongest levels. It is obviously stronger in level than the L/R channels and the LFE channel.
Once the importance of the contribution of the CC signal to the overall listening experience is understood, the answers to the questions about how the center channel should be reproduced become obvious:
* The center channel very clearly carries more than just dialogue. It carries everything intended to "image" from the front center of the video image.
* Because the CC carries the strongest signal, the CC speaker should be the strongest speaker, (or, at very least, the equivalent of the L/R's.)
* The CC speaker should be optimally designed, optimally placed, and acoustically optimized., (IOW, horizontal MTM's, installed badly, placed below ear level, near the floor, with a coffee table between the speaker and the LP... need not apply.)
* If you reproduce the strongest signal in the soundtrack through a speaker that is NOT the strongest speaker in the system, you will obviously be compromising the the most important channel, and therefore, the overall listening experience.
* If you redirect the CC content to the L/R speakers, and the L/R's are better, stronger, more full-range speakers than the CC, they will do a better job of reproducing the strongest content in the soundtrack than a less-capable CC speaker.
* If you redirect the CC content to the L/R channels, it is certainly possible to overload the L/R channels. Overload protection is required to ensure the L/R channels are not clipped.
Previously in this thread I described the attributes of the ideal CC speaker
. The above image reinforces the rationale behind those attributes. It may seem "ironic," but... a picture is worth a thousand words.