I would agree with you 100% on the headunit as that is the source of the audio and for a speaker to play all the frequencies loud is a big ask really so you need to add more so they can each do a part of the spectrum.
In the past I was playing with the idea of getting rid of the headunit as I use to use an mp3 player a lot and just plug the mp3 player straight into a four channel amp or via an active crossover. But then I just bought a decent headunit.
In the past I was playing with the idea of getting rid of the headunit as I use to use an mp3 player a lot and just plug the mp3 player straight into a four channel amp or via an active crossover. But then I just bought a decent headunit.