Completed my stereo upgrade and double din touch screen install.

[Starter986]

This is what I'm running, and quite satisfied with it.

https://www.amazon.com/Kenwood-KSC-SW11-Compact-Enclosed-Subwoofer/dp/B00BO8O9XQ

Mine is installed at the top of the passenger footwell, and covered by the floor mat. Perfect.

[Cunningr]

Here is a link to a guy make sub boxes the fit in the floor, really expensive but here is the link.
996/ 997 Floor boxes

I used a Bose subwoofer box from 996 cabriolet footwell, sealed it up and mounted an 8” sub doesn't bother the wife and does a decent job. Definitely not a earth shaker but notable low range support.