2014 Silverado with lifting sub box

[BarackYoMama]

Hey yall! 
 

Long time listener, first time caller here. After doing some searching, I figured I'd  make a post and ask. Has anyone come up with any type of under seat sub box for the rear seats that they've attached to the seats themselves? I'd like to get a little bit of added base to my audio system, but I typically fold up the rear seats when the dogs jump in. I'm thinking I may need to go the custom route on this which is no problem, but curious if anyone had done anything similar.