Sorry forgot to tell you that yes the "C" in the stereo/DVD is for the outside speakers. This is why you only need the video RCA connection. On the outside for dvd's. Keep in mind that if watching regular tv and not a movie, that you have to use the tv built in speaker.
TV: 2007 GMC 1500 Crew Cab 5.3L
Brake Controller: Tekonsha P3
Hitch: Equal-i-zer 4 point wd/sway control
Trailer: 2015 Cherokee 274RK
2011 Grey Wolf 26RL, 2009 Cikira 19 EXP hybrid, 2008 Clipper 108st (pop-up)