Dvd Deck For Vehicle If I Put In A 40 Watt Dvd Deck Right Now And Add A Amp Later It Wont Matter Right?

If i put in a 40 watt dvd deck right now and add a amp later it wont matter right? - dvd deck for vehicle

I try in a DVD player 7 "screen 40 watts X4 Jensen put my Dodge Ram 05th, but I know that this does not turn on the speakers much, but I think, get an amp later, and eventually anyway submarines it can compensate for energy is not there? thank you for your answer I need as soon as possible