'09 C5 stereo question

[GiveMeABreak]

The amplifier is integral to the RT4 motherboard, so I can't see that a realistic option to be honest. You'll either be better off looking for an RT4 second hand, or replace it with an RT5 which has bluetooth for example, or RT6 as an option, but all these will require VIN coding and possibly some configuration changes. RT does also need the High Res screen to operate.

[Milordas]

You mean that aftermarket amplifier wont work with my radio? Or do you mean that it's probably not the amplifier that causing the problem? You mentioned before that RT6 will need high res screen. Does that apply to RT5 as well?
I was looking for RT4 or RT6 on used car parts dealers, but they all seemed "tired" and some buttons missing the paint for the price starting from 250€ for RT4.

[GiveMeABreak]

Certain PSA vehicle Audio / Telematics systems could have the option of an equaliser amplifier as an optional extra - usually consisting of a separate subwoofer, the external amplifier and in some cases upgraded speakers.

Without this optional extra, the Head units rely on their internal amplifiers built into the head unit motherboard. As your vehicle (from the specs.) does not have the additional equaliser amplifier, then your amp is internal to the RT4. Now, having said all that, if your internal amplifier or the head unit is failing, then an external amplifier won't be any good at all, as it will likely use a speaker level output to convert it to an RCA pre-amp level signal. So if you don't have the output from the speaker to start with it won't be much use.

RT5 had the High Res Screen and USB socket on the C4 and C4 Picasso. It also provided Bluetooth functionality.

[Milordas]

I went earlier this week to French car mechanic to fix some issues and asked his opinion about poor sound quality from the front speakers. It turned out that my both tweeters are broken. They can still play music, but very silent and bad quality. He found some old tweeter in his garage, connected it to my car to test and sound became much more loud and clear. So I'm happy that my radio and amp are not faulty.
2 tweeters from used car parts store cost me ~50€ including shipping from Poland.

[GiveMeABreak]

That's relatively expensive....

Brand new dash tweeters from Citroen direct are only £19.45 each inc. UK VAT @20%., so may even be cheaper where you are.

[Milordas]

Hmm, I thought I had a good deal, because other options at other used car store was like 30€ for one tweeter as a starting price.

[GiveMeABreak]

Second hand parts are not always cheaper than new originals, plus there is the 'wear' factor and how much life they have left. I think people always assume that the dealer original parts will be expensive, which isn't always the case. In many cases the dealer original parts were cheaper than aftermarket parts!

Anyway at least you have found the cause and I hope they will last more than a week! (Just joking)

[Milordas]

Yes, very funny indeed That would break my heart