I have a “full” range speakers supported by 2 JL212 subs. The subs Integrated with the main speakers so well that now I cannot listen to the system without the subs. The quality of the subs is very critical.
I would disagree and say that getting the phase, crossover, sub volume, and room modes taken care of are more important than a high quality sub.
A few well integrated Dayton subs can outperform a hifi subwoofer that is much higher quality.
One of the reasons some hifi folks hate subwoofers is because you can’t just spend more to get better bass. Ironically more expensive subs can just amplify problems with the room and setup since they are so powerful.