OEM pioneer premium sound package
 

For those with the stock pioneer premium 6" sub that goes under the mat next to the spare tire, how is it exactly? What exactly is needed to install this if i didnt get it with the car?

i'm assuming you have a pre-2008 tc?
you would need the whole subwoofer unit and the wiring harness which connects to front speakers (and power, ground, remote). honestly not even close to worth it. the subwoofer sounds like sh*t anyways.

You can't have a sub with a 6" driver. That's just midbass lol.

Elemental Designs has an actual subwoofer that will fit in your trunk in the corner and take up very little room.

Get that instead if you want bass.