I have a Music Hall a15.2 integrated amp, musical fidelity v90 dac, and a pair of Elac debut B6 standmount speakers that I mostly use with a Chromecast audio or an onkyo c7030 cd player. This setup was great when we lived in a smaller apartment but now that we have a larger place the bass is (for my tastes) not as satisfying. Given that the amp doesn't have lfe or anything, what would the least obtrusive option be (quality-wise) for adding a powered subwoofer?

Here's a link to the amp manual as well: https://musichallaudio.com/wp-content/uploads/2018/04/music-hall-a15.2-integrated-amplifier-manual.pdf

Thank you!