I think part of the problem with manufacturers in general is that most centres are / were designed to be easy to implement and install. Designing them for placment above or below a display or on a shelf or rack limits the physical dimensions and weight. IMHO you can't change physics and the only way to get a "fuller" or "deeper" sounding centre is to use a bigger cabinet.
Like you, I have always preferred 3 identical mains across the front. Aside from their sonic characteristics being identical, their height is also identical, which is another dead giveaway when testing horizontal centre speakers. The only real fair way to test a centre speaker is to elevate it to the same height as the mains. This is why the dual centre speaker setup is intriguing, as users claim that the sound feels like it is coming from the screen as opposed to below it.
In my apartment I tried dual M22s above and below the screen and liked it a lot especially for movies. I didn’t mind it for music but it did mess up the soundstage on my best recordings a little bit but not to badly. The best sounding center I’ve had was a single M80 upside down above my HDTV. Having it upside down put the tweeters almost on level with my M80 mains but with the rest of the speaker extending upward it made the soundstage seem like it was radiating from the whole wall. The only thing it did to change the soundstage was to make the discrete audio like vocalist drums coming from the center sound like they were on a dais. I briefly considered using an AT screen so I could hang my center M80 upside down behind it. But then I got better. Sort of?
