To be fair I've never used any diagrams for speaker placement . Although they are handy as a guide.This has been some great input, and I'm convinced at minimum that 5.2.4 is going to be an upgrade worth doing. Already ordered another pair of Focal Dôme Flax (in white!) to make a front ceiling pair. Basically, as far as Atmos diagrams go (not Auro3D, I definitely can't make any of those work up here), they recommend these configurations (thanks, @Sal1950!):
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Where I'm at today matches the 5.1.2 exactly ('cept I'm 5.2.2). Moving to the right, I'm convinced of the 5.2.4 although my placement for the heights will have to be a little different (see below). I think I should still get the benefit. 7.2.4 is the question mark for me though, because I can't move the rears to where the diagram suggests, my room won't allow it (there's a stairwell there). So, that stacks the rears and sides pretty close to one another (like 3'-4') on the same plane (shown below), and that's where I'm wondering if the upgrade is going to make sense (because I'd want another pair of what I'm using for the rears and that, with stands, would run me like another $2500 so it's not a cheap experiment) and if there'd be enough separation to warrant it.
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Now, I could create another scenario with more separation but it doesn't align to any suggested placement models...
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I don't expect there are many of us who have the perfect room layout, or dimensions, to faithfully copy the advised speaker layout.
I've gone purely on space available and then used the Marantz to manually adjust each speakers output to suit my needs.