Could also be a problem with the crossover in the boot of the car left side behind the panel this splits the four chanel of the head unit for the 6 or ten speakers depending on what you have. Upgrading the head unit is easy just do a search on this site for related posts, I did mine and it works well I found a unit with changable display colours to and set it to match the dash but I would check out the amp/splitter in the boot first.