Hi. I´m thinking about to improve my audio system in my ID 3. It will cost me 700€ to put new speakers in front (Hifonics) and back (car rear tray) with an amply (the old school way, I mean, tying wires from front to rear). I´m not sure to do it because of the warranty of the car and the possible problems with the 12v battery. But from the other side, I miss a lot a good sound in our car. Any suggestion?FWIW, I'm happy currently* that I went the route I did, spent a bit more money but got a really good system for it. Comparing my factory system to my aftermarket system the biggest advantage has been that at higher volumes panels don't buzz and vibrate annoyingly anymore. They filtered it so most of the bass goes to the sub in the boot, and being able to turn the volume up as high as I like with no buzzing interior panels is a huge difference. Just adding rear speakers might have improved the sound a little, but putting in a sub and a proper amp has made most of the difference in mine I suspect.
*(I say currently because I haven't had to claim for anything on the warranty since putting it in. Remains to be seen whether they'd decline warranty work on the car now because of it)