One of the first things I wanted to upgrade on My Brera was the satnav head unit as this was not iPhone compatible. Changed this for a Pioneer APP radio with a 7" touch screen. The provided can-bus adapter worked fine, but the 2-din adapter was not. Had a local furniture builder make a facia ring.
Dynamat applied to the door panels, and now I discover the car has a Bose system..
More dynamat in the boot, and new power wiring for a new amp. Had a Pioneer PRS-D210 from an old spider. This can deliver 2x300w, or 2x600 bridged.
The Bose sub enclosure was also dynamited, and the attachment points got a layer of Auralex rubber. The reflex port was plugged, and the speaker replaced by a Focal Utopia 13WS.
Now the low end sounded MUCH more tight, and precise. and can go just as deep as the BOSE could.
As I sometimes play "loud music" I wanted to have a 10" Hertz Dieci sub-box as well. In order to use the amp in bridge mode, I wired the negative wire from both speaker to the amp. The positive wire was run to a two way switch button. One out to be refitted BOSE, and one for the Hertz.
If I have to use the boot, I can just take out the Hertz Box, and disconnect it with the switch. This also activates the Focal unit. (so I do not loose too much low end)
The next step is to replace the flimsy looking front speakers. Found a set from Gladen, 3 ohms resistance, and 94,75dB sensitivity should play loud enough, and sound far better then the Bose speakers.
also the slim line 165 SQX is a very shallow unit, so clearance should not be a problem.