With a good system imaging correctly a center channel is totally unnecessary and maybe even detrimental.
You can type this all you want to, but the math and science, and my own experience in motion picture auditoriums and my own listening rooms disagree, so good luck to you.
The positive effect is of course magnified for off-center listeners. A recording with a dense sound field and effects going around the room really show this off well. Another area that makes this clear is with otherwise unintelligible dialogues. There are a couple of places in LotR where dialogue is muddled unless the center is dialed in just right. Of course, there are discussions about why modern movies are sounding worse and worse, that's a separate topic. I am just saying that there are at least 3 important cases when a center improves things. Is it worth x dollars???? Tough call.
But as I have written, in your average modest living space, the effects are small, but positive. For a great thread on this subject which goes into the science and pros and cons, please read here:
https://www.diyaudio.com/forums/multi-way/277519-fixing-stereo-phantom-center.htmlYes, I have heard dedicated center channels improve intelligibility and the overall experience in your average living room. No, it’s not huge. If your choices are to get a poorly performing or poorly placed center without EQ vs. nothing, go with nothing.
I yield my time.
Best,
Erik