2020 Outback Limited XT Black on Ivory
Height is the biggest challenge under the front seats. I measured like 2 3/4" available under the passenger seat. I haven’t measured under the drivers side.The RF amplifier installed under the passenger seat so that space is already occupied. That is why I'm interested in putting a sub under the driver seat instead. I also tend to like to lower my seat as far as possible from years of driving sportier cars so I am a bit concerned about vertical clearance and making sure that I dont accidentally trash the sub when the seat gets adjusted by myself or anyone else who might drive it such as a friend or a Subaru service technician.
FWIW, I ran a $150 8" Blaupunkt self powered slim sub in my 07 ' Frontier for a while. It actually rivaled the sound quality and output of the custom 10" Pioneer shallow sub that eventually replaced it. I don't think they make that Blaupunkt model anymore but Crutchfield has a good selection and plenty of reviews. As I recall, there are a few other threads around where these are discussed.
ps. Silver, don't get me wrong, I'm not comparing the sound quality of all these systems, just the ability to know whats there. My HK system has been sounding pretty good (especially after 504) but it is what it is. I'm not sure I could just upgrade the speakers with sucess.