Hello qyy920,
I believe a good solution for any room and pair of main speakers would be to utilize at least a pair of subs in your room. You could use a pair of Dyn’s own Sub 3 ($1,799 each=$3,598/pr.), Sub 6 ($2,799 each=$5,598/pr.) or a pair of REL T9/I subs ($1,099 each/$2,198/pr.) but I would suggest a pair of SVS PB-1000 subs (currently on sale for half price at $499 each/$950/pr.) will perform just as well at a bargain price. Here’s a link to these subs:
https://www.svsound.com/products/sb-1000#tab-2
Despite the bargain price these are very good quality subs that have all the necessary controls such as line level and speaker level hookup options along with controls for volume, crossover frequency and continually variable phase settings. Like the other subs, you have the option of using the built in high pass filter to restrict the bass output of your main Confidence 5 speakers or running them full-range and supplementing their bass with the pair of subs below a specified bass frequency through low bass filters on the subs.
I wanted to make you aware of these bargain priced subs but I’d also like to know more about your room and system to better tailor my advice to you like:
1. Your other system components by brand and model number.
2. Your exact room dimensions.
3. Where your main speakers and gear are located, along the long or short wall.
Thanks,
Tim