2007 mazda3 stereo replacement

I have a 2007 Mazda 3 with a fully integrated stereo, for lack of better words. It has a Bose sound system which sounds pretty good but prevents me from installing sub woofers because the head unit doesn't support it. Now in a normal situation you could just remove the stock head unit and replace it with a new one. However, as far as I know, this is not possible with my car without(in my case)completely destroying the interior. What Im getting at is, is there anyway I can still hook up sub woofers without changing out the head unit. My buddy said there was some kind of filter I could use to run the speaker input directly to an amplifier while still keeping quality sound through the woofer. I don't know about half the stuff he says but I could be wrong. Any ideas? Thanks.

of course, what you need is called a line output converter. it steals a signal from your existing speaker wires and gives you a set of RCA outputs that can be used by any amp. the easiest place to install one of these is at your rear speakers, this will also save you some money by not having to buy a long set of RCAs to reach all the way to the front to the back where your amp will most likely be.

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Alright, so if I were to do as [i am an idiot] showed me, I would be losing the display that shows my climate control information and all that jazz, correct?