I haven't heard the Continuum A.D. MKIII, but have heard the S-9. The S-9 sounds absolutely fantastic, they sound immensely big, and I heard them play low compression pre master big band at live levels in a small/medium hotel ball room sized place. They didn't miss a beat and threw a big sound stage with big swathes of sound images, similar to what I hear in real life.
However, I would have to go with the Continuum, from what I know. It should offer refinement all the way around, except possibly speaker disappearing. The cabinet is built like the rest of SP Tech's Millenial Reference series, i.e. with constrained damping/hybrid t-line. The S-9 has a cool layered and rigid cabinet but lacks the hybrid t-line, afaik.