If you haven’t been driving it for at least 150 hours with the system on, it WILL improve. Takes forever to burn in but it does actually get quite a lot better than on delivery, well above and beyond psychological acclimation (you can A/B compare new and used and tell)Did just that, not much difference if any.
Overall, I would say this amp/sub addition is an improvement but nothing to shout about.
Premium audio it is not.
To my ears, the sound is generally tinny despite the tone settings. Tweeters must be low-quality.
Drivers in the trunk are clearly AM-tinny and bright.
Anyway, the amped sub helps some...