I have a 02 tl type S and I want to change out the head unit and speakers. I was told that if I do that I have to rewire all of the speakers in the car. Does anyone know if this is true? I want to put subs in the car but don' want to rewire the whole thing.

 

headunits usually have speaker wires coming out of the back...you then solder or crimp the wires with the speaker wires in the dash. Not really, re-wiring, more like matching up wires...crimp "Left" with "Left", "right" with "right", etc.

with a sub; there are a few ways you can do this.
you can tap into the rear deck signal using a line out converter, or plug aftermarket amp directly into stock amp.

technically, you're not "Re-wiring" everything.....but technically, you are installing a new speaker(subwoofer) which needs to be wired

 

Are there any plug and play speakers that can be used to upgrade the door speakers just to get higher quality sound from them? I wanna keep my head unit stock but upgrade the speakers if that's possible.

 

Most 6.5" speakers will fit the front doors without modification but you will need 1/2" spacers for the magnet to clear the window or you can use 5.25" with an adapter.

The rear door openings are slightly smaller and will usually need require some sheet metal cutting for most 6.5" speakers, however, with a little research you can find some that will fit without cutting. 5.25"
once again will work .

Speaker upgrades will definitely sound better than the stock Bose, but if you really want to hear their true potential then you will have to bypass the factory EQ which is tuned specifically to the crappy
Bose paper speakers. To bypass the EQ you need to pull the head unit and do some wire cutting and splicing.

I scrapped the factory HU and went aftermarket, along with some decent amps, 6.5" components all around and subs.