I'm still reluctant to believe that someone who isn't an audiophile would find it worth it to upgrade from "good" speakers to "great" speakers. Sure, anyone would benefit from a $400-500 upgrade from 15 year old worn out factory speakers to a sub, component speakers, and rear 6x9s that don't spit and crackle, but I can't believe that it would ever be worth my while to pay 3, 5, or even 10 times that to get the top of the line.
It's a car audio system. Even with a great sound deadening job you're going to lose the finer details to the engine noise, especially in our noisy vehicles. Maybe someone with a Tesla could benefit from dropping on big brand name stuff, but I refuse to believe it's worth it for anyone who doesn't take audio extremely seriously. I've actually met people who trash low end audio systems and then drive around with the windows down listening to name brand systems. I guarantee they can't hear those extra $1-2k under those conditions.