I have the common stock sub rattle in my TL. I have the factory head unit still and all factory speakers. I was interested in doing the kicker 8" upgrade with 5 channel amp upgrade. I came across a video from mobile max audio where they put a 10" or 12" down-firing kicker in the trunk instead of doing the 5 channel upgrade. This route seems appealing since I wouldn't have to worry about rattle and can have a bigger subwoofer. Although I have a couple of questions.

Is the sound quality and volume decreased because the subwoofer is all the way in the trunk?

Would you recommend the 10" down-firing kicker or the 12"? Assuming I am keeping the stock amplifier for speakers and stock speakers.

What amp, LOC, and Wiring kit would you recommend with the down-firing kicker sub?