Hows it going everyone!

I have a 2011 VW jetta Sportwagen that I'm considering putting some sort of sub in. Nothing too crazy, probably just a 10 inch something. I'm hesitant for a couple reasons.

Firstly, I'm worried how the bass will affect all my trim panels and other components. I just rolled over 75 k miles, and so there's already some looseness but i'm worried that with a sub my car would be rattling all over the place and would start to fall apart. Is this a fair assumption? If this would happen, how easy is it to prevent/repair? Is it something that I just will have to accept if I do choose to drop in a sub?

Also, for my VW fanboys out there, I've been looking for the best way to mount a sub without loosing cargo space. Ive been looking at boxes, and was wondering if there was one that took up one to the side cubbies in the back. I've seen boxes like that for GTI's, but never for a Sportwagen. Any leads?

Thanks yall