i installed a pioneer double din head-unit in my Z last year and had major problems with the loudness, its a problem with the signal being sent to the bose amp from the head-unit. some people install a signal booster but i had problems fitting it behind the head-unit so i gave up in the end haha, all i use now is the bose head-unit with the iPod hack, cant go wrong as i use spotify on my phone and just plug it in sounds pretty good also!