why wouldn't you just put one side on the sub, and one on the carpet?

 

Old post but i see people talk about running power through the rubber grommet by the brake pedal. I found the gromet but I cant get the power cord to go in, do i need to drill? I cant get close enough to see very well thanks!

 

I fit a 4 Gauge power wire and an 18 gauge for something else i was doing through the hole fine...

Bigger then 4 GA you probably need to drill the hole out a little.