On the premium system
-1.5, -1, 0, -0.5, +1 is the most balanced curve I’ve found so far.
The “sub” is not a sub so boosting it means you are just increasing distortion, it will be more boomy but not necessarily better bass. You can’t ask an 8” driver to produce true low end air movement cleanly.
The midbass are not mounted with sufficient rigidity so by increasing you are just introducing resonance through the car materials not improving “punch”
The midrange lacks a bit of body but has pretty good clarity, certainly very good for a factory system
The highs are constrained from factory, I am investigating options.
Try what I’ve posted above then turn it up louder. You will see I have a reference point of 0 for one band, always cut instead of boost if possible and never boost a lot next to where you have a cut or vice versa.
Cutting can actually increase the overall oomph of a system, it’s a pretty typical American preference to have thicker heavy low end bass which is not really that natural but of course everyone’s ears are different and some folks just want to set things to extremes - which is also fine - but not my preference.
But definitely don’t kid yourselves that going +5 on lowest band is a good plan ..... it’s asking an 8” speaker to distort itself to death.