Without having experience to compare with others, I have a set of four speakers, two 6.5 in the doors and two 6*9 in the shelf. I added the amplifier and a slim woofer 10', and the result is chaotic, very good quality and intensity compared to before

Although I am not an expert, with good Hertz speakers, the result is amazing. I have a Chinese Android unit (Android 10 GPS screen...) and I have the volume slightly above the middle as it can handle even larger speakers than it seems. My speakers output about 600 watts in total. What is important is the bass, opening it from the amplifier gives you full coverage. It can also take an extra 300-watt subwoofer, but I haven't installed one. My speakers produce satisfactory bass (Hertz CK 165L). I didn't choose newer and cheaper ones because they don't produce the frequencies that this one does. For me, besides the fact that it consumes a lot of battery and if the car engine is not running, it drains it in 2-3 hours, it is flawless. I will get a battery with more amperes, etc., and it will be even better. I recommend it.