Hello, so heres a thing. I currently have Audi 80 Avant 1.9TDi and I want to do an audio upgrade. Big 3 update was already done, I even found a subwoofer wires in the trunk ( car is from Germany, so it means previous owner had something in that ). So I want to upgrade my front/rear speakers, because front sounds awful, and rear ones doesn't event exist. I have enough budget for it so I need some advices. One of my friend suggested me to buy a 4 channel amplifier(4*100rms or 4*150) for this setup, use a crossover ir front ones and finally install something in the rear doors. I have a piooner's headunit, which handles 4*50w. So, what should I do? Is it a good idea?