Down fire subs in rear bench seat?

Hello all, first time poster, long time reader. I have a 2020 double cab Tacoma, no JBL package. I’m contemplating options for adding bass to my sound system without sacrificing space. I’m not against using behind the back seats, or under them, but would be nice for one or the other (not both). But that leads to another issue in my mind. I Haven't heard what it sounds like to have speakers in either of those locations with the back seats in their normal positions, but I’d imagine the sound quality is not to good. Even with removing the plastic backing of the seat. Given that I need my back seat functional, that leaves two options. Rear fire behind the seats, or down fire underneath the seats. Using dynamat or the like, and possibly venting (under bench). I’m amplifying and upgrading all stock speakers, so mid and high range will be good, just need some decent rumble options. Any thoughts, comments or experienced insight is greatly appreciated. Thanks