For folks that have mounted an 8" sub to replace the factory 'sub', how did you go about that? I am wanting to put in a Polk MM840, and intend to build a sealed enclosure and mount it to the bottom of the rear deck. I was considering doing a free air (IB) sub but would still need a way to isolate the rear 6.5 speakers. Since there are 2 of those but only 1 sub, I figured the easier way tot go is to box in the sub. Its a 0.35 ft^3 volume box, seems like it should be easy. Am I missing something?

 

you have to defeat the Active Noise Cancelling (ANC) feature (if applicable), you have to add an external amplifier - the stock amp can't power anything worthwhile, and you should consider decoupling the enclosure/sub from the rear deck if you don't want it to rattle like hell.

the amp you get should have auto turn-on and high level inputs. Kicker, Phoenix Gold, JL Audio all make amps like this.