Also use surround mode which seems better. Replace the sub though as that makes a night and day difference and is so easy to do.
That Pioneer model suggested on this forum is so powerful on max settings it rattles and makes parts vibrate in my interior. I used to have 2 12's when I was younger, IMO that sub replacement is pretty solid. Definitely a plus to not have to re-wire/change everything up to get some nicer bass. I usually run it at about 75% bass level now.
I run mine on minimum which is just right for me ! Other threads on here mention the 60Hz 'hole' in the car which the OEM system is boosted to fill. It is interesting how the sound is impacted by driving along compared to standing still - the effect of road noise, especially tyre noise from the rear. I added extra sound deadening in the boot / trunk which helped as well.