2005 Acura TL Base (Non Navi)

Rockford Fosgate P3 2x12
American Bass 4000W Max Class D Amp

Will I need to get an aftermarket stereo for this combo?

i was told I need to get an RCA converter since I think our HU does not have an RCA and has a 40 pin harness.

Basically, will I need anything else to run this sub and amp combo?

 

There is a lot of attentuation of sub frequencies if getting signal after the stock amp. Better idea is to connect to the preamp signal from the head unit before it. Below is copy pasted from an old stickied thread...

@ the Stereo Amplifier in the passenger kick panel in the 20 pin Black & White connector

RF+ Black
RF- Gray
LF+ Green
LF- Blue
C+ Brown
C- Greeen w/White
RR+ Orange
RR- Red
LR+ White
LR- Yellow
SW+ Red w/Blue
SW- White w/Green

Remote Turn-on -> Red w/Yellow
Amp Mute -> Yellow w/Green

 

but, the answer to your question is, absolutely not!