'04 209 command replacement
1. The dash will hold a double-DIN unit. You will need a trim plate adapter, but they are readily available. As long as the new unit is not exceptionally deep, you should have no problems there.
2. You can get a "plug and play" wiring harness fore the vehicle (many eBay sellers offer a kit with the harness and the faceplate). However, it is missing any connections for accessory power an illumination because the factory system gets these signals through the CAN bus. Also, it will have wiring for the speakers, but the vehicle's harness will not have those so you will need to run your own analog wiring to the trunk.
3. To get signals for accessory power and illumination, you can tap into the wiring harness feeding the ashtray - it has both. Another option is that there are some CAN bus adapters that give you steering wheel control and also offer those signals. Some also offer a signal for reverse gear in case you want to add a backup camera.
4. You will need to replace the Bose speakers. First of all, they are 2ohms, and few amps can drive that. Also, without the specialized equalization from the Bose amp and head unit, they will sound terrible.
My advices: Replace the head unit with a nice aftermarket touch screen NAV, run low-level analog wiring to the trunk, remove the Bose amp and add your own amp in the trunk, replace the speakers.
Get a CAN adapter, that will give you steering wheel controls etc. Get 1 or 2 amplifiers (depending if you want or have that center speaker) and run wires to the head unit. The Bose speakers will sound just fine. You can retain all of them including the sub as long as you get the right amps.







