A couple of years back you guys mentioned I should change the head unit if I want anything to sound good.

I have educated myself and technology is changing so I have this questions for those who know more than me:

Can a line processer like this be used to 'process' the signal from the stock head unit before it is routed to an aftermarket amplifier and speakers ? Do these processor solve the variable impedance from the stock head unit so that everything downstream can be feed at 4 Ohms impedance ?

https://www.crutchfield.com/p_161LC7....html?tp=70736

This guy never mentions once the impedance settings of the system he is setting up. He talks a whole lot about gain and voltage. Is it the same as adjusting resistance (Impedance) but from the other side of the V=RI formula ?

https://www.youtube.com/watch?v=hGVJcn8lASs

Thanks