It’s mostly the amp. I too have OBs, in my case Emerald Physics 3.4s (concentric 1" polyester in a 12" woofer) and my room is ~ 35 x 20 x 12’ peak in an open beam ceiling. Front wall is ~ 80% glass and rear wall is 100% glass. A tough room to get thumped in. I tried using 2 SVS barrel powered subs, which I bought new 10+ years ago. In those days they were focused on HT, and these sucked for 2 channel. I sold them about 2 months ago, and my musical enjoyment is the better for it, but, no deep bass, and missing a bit of the muscular musical scale. By far the 2 biggest changes I made were replacing my EVS 1200 class D 600/1200 wpc dual mono amp with a LSA Voyager 350 GaN amp. And although the V has ~ half the EVS’ power it is actually a lot more room filling. The other addition, which significantly improved low end (as well as the rest of the spectrum), was replacing a Marantz HD CD-1 that I used as a transport with a dedicated transport- Audiolab CDT 6000.
I still want what good subs can bring, but the cost to do it right is elusive to my retired SS budget. HTH