I don't think I've ever seen a car audio system without an external amplifier of some sort. This article does a good job of explaining the difference between the two. The devil is in the details when it comes to power (max vs rms, advertised vs real, etc) and advertising is an evil devil when it comes to"power ratings". Just paruse Amazons selection of 1000w about that actually will run 200ish Max output. Should it be simple to design a sound system based on trusting the manufactures claimed outputs? Absolutely! Is that the way this game really works? Not at all.
https://www.crutchfield.com/S-MahHPK8AyuS/learn/reviews/20030722/power-power_comparison.html
I'm only telling you this to save you time and frustration. I'm no expert in audio equipment but I've wired enough systems to know this stuff. When I recently installed rear speakers in my 986, I temporarily wired them directly to the unit for ****************s and giggles. It's a boss head unit with a built in 50x5 amp, you couldn't even hear the sound out of the speakers. In order to get good sound on 4 50watt pioneer shakers weird on 2 channels, I had to use a 1000w pyle 2 channel amp at 60% capacity to match the factory amp output intensity.
Btw, the reason you're not happy with the door speakers is because the factory amps have a built in low pass filter for those outputs, which couples with the boxy enclosure, is supposed to emulate a subwoofer. They don't, obviously, but that's why.
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