I can agree somewhat to larger bass drivers in speakers should add the lower end without a sub but that’s not always the case. My room is smallish, 13 by 15 and my Wilson Watt/Puppies with twin 8” bass drivers can overload the room. When I switch to planar speakers, Quad 63’s or M L CLS’s, I then use a subwoofer with a 12” driver. It’s an older Velodyne but blends very well with planers in my room and fills in the low end just about perfectly. And as others have said, your going to pay big for larger integrated woofers into a speaker, no way around it, larger woofer, larger cabinets, more crossover components. I guess I’m lucky that I don’t have a huge room to fill with sound and don’t really have the need for larger woofers. I would think the OP’s Wilson Sophia’s would have adequate bass slam as most Wilson’s have it in abundance.
Demise of bass quality in Main speakers
When I was shopping for new speakers in addition it became quite clear that modern day main speakers are being made with smaller bass drivers. And to get larger bass drivers you have to go up to alot more expensive models and still they or on the small side.
The Industry came up with a solution for bass challenged main speakers - buy two subwoofers to solve the problems of the modern age main speaker. And subwoofers now being sold in pairs have 8 inch or 10 inch driver sizes, which are still not big enough unless you spend a lot more money.
I bought a subwoofer with a 12 inch driver 20 years ago, thankfully. When I looked at the newer subwoofers the speaker manufacturer told me that he gets many comments stating that the fullness and rumble ability of modern day subwoofers have been substantially diminished, and he agreed. Isn’t this what subwoofers are all about. Why would I need a subwoofer for better define the lower base area. Fortunately I bought very nice main speakers which had a range spec down to 20 Hz and the bass driver size is 8 inches but I had to pay more to get this larger size.
Why do people put up with this? Put larger bass drivers in Main speakers and then you won’t have as many people complaining about Poor bass quality. Doesn’t this make sense?