Hi Texas:
Here are a few thoughts based on considerations I've given to my Duntech Princesses, a close sibling to your SC-IVs.
1. I agree with the criticisms of horizontal D'Apolito arrays for center channel
speakers. For anyone not on direct center line with the tweeter, they will receive an unbalanced sound. The overwhelming existence of this design in the marketplace is a function of practicality to fit into furniture (as in your case), not sonic presentation.
2. You did not specify if you want a home theater set up or surround for music, or both. To optimize tonal balance I would try to buy the same or similar model tweeter and midrange drivers (one each) as in your DAL. Then I would get assistance in crossover design and cabinet plans from the speaker supplier (Madisound or PE should both help with this). Then I would construct (or have built) an enclosure that could be placed a little above floor level and angled back to project toward listener head height. Placement close to the floor should give a small bass boost to compensate for the smaller size of the mid driver. And if dialog is your primary interest for center channel, extended bass is unnecessary. I would keep the mid and tweeter in a vertical array -- NOT horizontal (meaning only one mid). This may not be a perfect match but should be similar to your SC-IVs. Such a speaker would be small enough to be easy to move when not in use if it is objectional to leave it on the floor all the time.
3. An easier answer would be to find a sonically similar center channel already built. Since I do not agree with the horizontal D'Apolito array, I would not bother with looking for a DAL center channel. Because the Vandersteen speakers are designed around similar criteria -- time and phase coherent, including 1st order crossovers -- as Duntech and DAL, I think one of their center channel speakers could work out fine. In addition to the design similarities, Vandersteen uses a coaxial mid and tweeter in all but their top line center channel models so they are more compact. Thus placement may be easier.
4. My last point is a very personal one which is why I offer it last. For music listening, I would not bother with a center channel speaker with any of the Dunlavy speakers because of their already outstanding soundstaging abilities. Why muddy the water? However, for home theater systems with DVD dialog steered to center channel, I would look for a small, high quality speaker like the Vandersteen VCC-1.
Anyway, good luck in finding whichever answer satisfies you best.
