On my MY22 PlusFour the kenwood amp is in the panel behind the speakers. Incidentally the Bluetooth receiver unit is under the glove compartment at front of car. Photos attached if helpful, BTW easing out the panel clips along the top edge (see 2nd photo) needs some care.

Gonze,
Your car is the same as mine- as there is no fader facility in the standard setup and very little volume from the front speakers, I installed a pioneer radio in the panel to the right of the driverssid speaker. I connected the radio to the amp instead of the musicstream unit. I now hav full fader control via the radio and all music from my phone through the Bluetooth connection to the radio. Pioneer provides an app to remotely control the radio via my iPhone. All problems solved!!

Hello Gonze,
thank you very much for the pictures. Such pictures will certainly help all CX owners to solve problems with the Bluetooth 👍
Which Pioneer radio did you use? I have picked out for me the SPH-10BT.

CLPlusfour, it was me that fitted the radio - it is a Pioneer MVH-S410BT - the BT bit is important as this signifies Bluetooth. I think this is now superseded by the model MVH- S420BT - either will work fine . You then download the app “ Smart Synch” to use the phone as remote and thi also allows remote adjustment of the radio such as fader etc.
I am presently on holidays in Austria so do not have access to the photos of the install but it is fairly intuitive- just connect the radio output via MCA lead to the input of the amplifier instead of the Musicstream leads

Cheers from Austria(with no snow☹️)

Sony DSX-A510BD is another Bluetooth capable radio that can be controlled by their app on smartphone for DAB/FM reception. It also allows music streaming, Google maps voice directions (very useful) and hands free phone with optional external mic.

We upgraded our Bluetooth sound system to an Alpine unit of much higher quality and functionality, with new high quality speakers (Alpine, rear only).
So much better than the pretty rubbish system originally supplied in the car but I don't listen to it much anyway as it is difficult to hear over over the B58 and I need to concentrate on not crashing :-)

P.S.
The Alpine unit has a built in subwoofer that greatly improves the sound when you can hear it.

You connect the radio to the amp, but dont you need a 12v supply line?

Thierry,
Yes you do -and an earth, but I didn’t want to insult the poster’s intelligence!!😄😁

Sorry Robbie enjoy your vacation in Austria There should be good snow at the moment only in Ischgl as far as I know ... and thank you all for your information