Are you not wanting a horizontal center? Just curious about your thought process there.
The difference between the SuperSong Surround and the ST Monitor is pretty minimal, and with the ribbon up top, I think you'd be fine. My main thought is in Mid-range performance. Admittedly, I've always said I'd take a Dennis Murphy 2-way over many other 3-way designs. But I also consider that might be the kicker in a good voice matched center, too.... Hard choice. Is a third Song 3 Tower not in the cards?
I think you would be solid with with either of those 2-ways as a center channel... The guy who invited me in to audition his Phils had an early Song3 Center, and he loved it, fwiw.
(BTW, unless you've got a Savannah, or a large Maine Coon, chances are they aren't moving that 26-28# speaker. With a non slip pad of some sort, I don't think it would go anywhere.
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