The box is in my garage with amp but I still own my 2010 and can mock it up for you
So here's how the jl 500/1 fit under the seat, I believe I had to remove the padding underneath for clearance issues, and fished the wires to the back side, while cutting slits in the carpet fit the wires. When installed, you do not see the wires.
Here's my dirty old box.... It's a 12, I also had the 10 inch version, but I kept blowing the speaker so upgraded to a 12.
This is it between the captain chairs
Here it is with the armrests down
My set up was I tapped it into the factory system using an audiocontrol LC2I, It got it's remote from the GM lockpick (which has a remote wire that's not hot when engine is off), I snaked the power wire connected to a circuit breaker, through the factory hole in the firewall, and RCA's on the opposite side (coming from the LC2I). The wires were tapped into the factory sub woofers leads (I forgot if it was before or after the amp, but I remember one way didn't work). Also I had to remove the "microphone" from the noise cancelling system, so that it wouldn't give crazy feedback. Sorry for the dirty car, I gave my 2010 to my mom so she can pick up my daughter from school, and she makes a mess of the car. My 2017 is my daily. (my daughter has a things for esky's)
BTW, the back of the box can sit about an inch lowed if you push the box forward a bit. There's a slight lift in the carpet the further back you go.