Which system for beginners (Audi)

Good day, I asked at the Audiforum how and what I should get. I was referred to you because you are the experts! So, my plan is as follows: I drive an Audi 80 with the original LS and the original Panasonic Radio. This combination is just tolerable to listen to the radio. Everything beyond that is unacceptable! So new clamots have to come here! I don’t need sinfully expensive high-end equipment. I just want to hear some louder and with good sound music while driving. I hear rock and electronic music (House, Trance). The problem with this is not only that I have no idea about car-based building and that the conversions have to run minimally invasively. The Audi is not mine, therefore I can’t do all the conversions. So for the beginning new LS have to go in front (10cm) and a new radio. These two things should fit together. But since I don’t know what I have to pay attention to (Watt etc.) I ask you *gg*! Otherwise it would be nice if fachc German is spoken (2-way, 3-way, active, WATT…hääää?!) to me a short explanation is given hehehe! Price should at least the LS not be more than 100euro. Furthermore, I am happy for suggestions, how I can increase the sound experience (more speakers etc.) open! So at this point thank you for having fought through the long text! MFG The Audi from Oppa