Welcome to the dark side. The answer to your question is, it depends on what your goals are, what you listen to and how loud you listen. If you prefer aggressive bass driven music, like blues, rock, EDM, and even modern country, specially at higher volume levels, bigger will be better. Be warned. A good subwoofer system will expose room node issues, which is why more is better than less, up to four.
I would read this before doing anything.
A great subwoofer system can be immensely rewarding, they can also be immensely frustrating. I have been using subs for decades and much to my chagrin, I’m still learning.