Hello,

sure you can change the speakers, but you have to use complete new wires.

Are your old bose speakers damged or do you want to use a new car radio.
For using other radios you can take different adapters but different car radios need different adpters, the most used is the "Dietz 17008"

If the speakers are damaged, mostly are only the amplifiers are damaged. Every speaker has its own small amplifier, it is a small green circuit board inside the speakerbox.

In Germany you can order replacement kits, one for the front and one for the rear, both kits contain two amplifiers, one for the left and one for the right speaker.

Part Numbers:
Service Kit front: 441 035 381 A
Service Kit rear: 441 035 382 A

The price is around € 85,- for one kit, € 170,- for both.

regards