I upgraded my S-2 center to a Duo. It's a marked improvement. The Duo center really punches above it's weight class. It's quite impressive, the Duo is.
Search around the archives here -- I believe that Dave has said that the Duo is a better center than the S-2EX under most circumstances.
That said, I'm also running with a pair of Rythmik LVX12 subs using 80 Hz xovers with everything. The subs also make an improvement in both dialog and L/R. Don't make the mistake of thinking that subs are only about the bottom two octaves or so. They also cleanup the midrange by doing the heavy lifting and therefore lowering the workloads on the other speakers.
Back to the Duo, my wife gave me "that look" when I upgraded to the Duo. But she had been complaining a bit about not being able to understand dialog in some of the TV series she was following. Even with a +2dB bump on the center channel. But she immediately took to the Duo, cured all of her dialog intelligibility problems all at once, and restored balance to the system at the same time by returning to a 0 dB bump. And neither she, nor I, have felt any need for a better center since I dropped the Duo in place and re-ran Audyssey for it. It's so good that she now denies ever giving me "that look" in the first place.
So... will it work for you? That's what the in-home trial period is for. What have you got to loose?