Hi Jonathan. I owned Duntech Princess (older sibling to the DAL SC IV) for 19 years and have four friends who also owned or still own that model. Based on that I've had quite a bit of experience with rooms, placement, amps, etc.
I absolutely agree with your recommendation to add a subwoofer. While the Princess and SC IV have very decent bass response by themselves, they (like most full range speakers) can benefit by the removal of the bottom one or two octaves. As you suggest, this is more to benefit the upper bass and midrange than for bass extension. I did not have room to add subs but two friends did and both the Vandersteen and Velodyne subs can be made to match very well.
A few thoughts on placement. First, John Dunlavy often recommended long wall placement for his speakers. I believe this was because of the need to keep them away from sidewalls. Second, he recommended an equilateral triangle placement between speakers and prime listening spot. Taking a clue from the Owner Manual, factory frequency response measurements were made at a distance of 3M to allow integration of the drivers. Based on this, I feel that 10-11 feet should be optimum distances for the triangle. Third, I did extensive testing for smoothest bass response in my room and ended up with the front baffle of the speakers 44" out from the front wall (your distance may vary, depending on room characteristics). And fourth, I found toe-in with drivers pointing 2-3' behind my head (inside cabinet wall just visible) to be best.
Don't ignore listening height. The D'Apolito array means that vertical spacing is just as important as horizontal. Try to have your ears at the same elevation as the tweeters.
I think the question of spikes, platforms, etc. will be dependent on floor composition (wood suspension, concrete, etc.), floor covering, and amplifier choice (with resulting woofer damping).
I still consider the Duntech and DAL speakers to be among the best available. But they are very revealing of set up and component matching. Spending the time to optimize both for your situation will be musically rewarding.
I absolutely agree with your recommendation to add a subwoofer. While the Princess and SC IV have very decent bass response by themselves, they (like most full range speakers) can benefit by the removal of the bottom one or two octaves. As you suggest, this is more to benefit the upper bass and midrange than for bass extension. I did not have room to add subs but two friends did and both the Vandersteen and Velodyne subs can be made to match very well.
A few thoughts on placement. First, John Dunlavy often recommended long wall placement for his speakers. I believe this was because of the need to keep them away from sidewalls. Second, he recommended an equilateral triangle placement between speakers and prime listening spot. Taking a clue from the Owner Manual, factory frequency response measurements were made at a distance of 3M to allow integration of the drivers. Based on this, I feel that 10-11 feet should be optimum distances for the triangle. Third, I did extensive testing for smoothest bass response in my room and ended up with the front baffle of the speakers 44" out from the front wall (your distance may vary, depending on room characteristics). And fourth, I found toe-in with drivers pointing 2-3' behind my head (inside cabinet wall just visible) to be best.
Don't ignore listening height. The D'Apolito array means that vertical spacing is just as important as horizontal. Try to have your ears at the same elevation as the tweeters.
I think the question of spikes, platforms, etc. will be dependent on floor composition (wood suspension, concrete, etc.), floor covering, and amplifier choice (with resulting woofer damping).
I still consider the Duntech and DAL speakers to be among the best available. But they are very revealing of set up and component matching. Spending the time to optimize both for your situation will be musically rewarding.