Hi Ajax,
You stated:
"Yes the only way to ensure a perfect match of left main, center, and right main is to use the exact same speaker in all 3 positions."
I'd preface that comment with "In theory, the only way. . .etc."
But in reality, the vertical center that's identical to its two mates at the front will still be subject to all the vagaries of placement (boundaries, the TV screen, walls, etc.) that prevent any three identical speakers from sounding absolutely the same, at least using a pink-noise test signal, when they are in slightly different positions in the room. Noobies are often puzzled why their speakers sound different when fed a test signal like pink noise.
The real test is whether through experimentation with placement you can get the center and the two mains sounding enough alike that with movie soundtracks or music there are no tonal or timbral deviations that will distract you from enjoyment of the music or movie.
Regards,
