My advice with subwoofers: the wrong subwoofer won’t integrate well and/or won’t really improve or add much to your system’s overall sound. The right one will integrate cleanly and completely transform the sound of your system to a level you could not have imagined. Take this from a guy who has played A LOT with A LOT of different subwoofers over the years.
And it’s not just about the brand. That can tell you nothing sometimes. For example, my dad, who has a pair of Magnepan LRS+ quasi-ribbon floorstanders, started off with a Rel Tzero. It added nothing to his system. It’s a toy, not a proper sub, Rel labels on the enclosure notwithstanding. Waste of time and money. But jump up to something like an HT/1205 and now suddenly that’s a serious sub. This can transform your system.
I am not sure how far your speakers extend down in your room, but you would be absolutely surprised at how much music actually exists below 30Hz. Additionally, many speakers, especially smaller standmounts, while capable of output approaching 30Hz, will begin to compress and strain to get down there, affecting the quality of sound higher up in the spectrum and inducing problems like intermodular distortion. High-pass filtering your speakers and allowing the subwoofer to cover that higher energy bass can dramatically improve the quality of your speakers’ output from just this alone, even more so if you have ported speakers and seal the ports since they’re no longer needed to boost low frequency output.
-Ed