there isn't really such a thing as a built in amp in decks .. if u want good sound u pretty much always need a seperate amp to play loud music ... with a proper amp, not those cheapie boss shit ... well maybe the boss shit if u've really god budget problems ... the sound will be much much clearer once its turned up!!! and heres a bit of advice ... with car audio .. u usually get what u pay for ... so spend that little bit extra and you'll be much much happier