upgrading

"upgrading" from a single zv5 15 to two xv3 12s. Been running on an SIA 3500d, looking for something reliable north of 5k without obliterating my bank account. *I do not need the best of the best

A friend purchased a new 2024 Kia Sportage, and he's dissatisfied with the car's sound system (Came with a basic 6 Speaker System - Not Harman Kardon 8 Speaker), intending to upgrade it using a subwoofer amplifier and speaker amplifier from his previous car (Alpine S-A60M + Rockford Fosgate...

So I have a factory amplified system. I've decided I want to upgrade the whole thing. I don't want to retain anything from the factory system. Would I be correct in assuming that when I get a new head unit. And my own amps for the sub, replacement speakers in factory locations, and some...