Cheap, easy sound enhancement in Focus Mk1

Available situation: car radio from Kenwood (KDC-120UB), compo-system Eton Pow 160.2. Nix insulated, no amplifier. I’m not satisfied with the sound – the tweeters are simply too pushy. Was also with the previous compo-system (Pioneer TS-E171CI), only that with the at least the TMT was even better. Music is heavy metal, I don’t turn up loud (highest half volume). What alternatives are there? The original speakers are not! And I don’t want to spend too much money (about 100 euros, because of me it can also be used). And it should be a plug-and-play solution (so don’t put something together yourself). Koaxe? If yes – which would be recommended (16 cm, round)? My hearing is unfortunately sensitive with regard to high tones – I perceive the at a certain volume as unpleasant (hyperakusis), moreover I have tinnitus. And since the Focus Mk1 series As a result, there’s no built-in space for tweeters, it’s only on the door door – where the tweeters then scream in my ear… It’s really all about listening to music in acceptable quality. A little louder than room volume. Without much effort, since I don’t drive the car for a year anymore.