But what did the vehicle come with as a configuration? Dodge intrepids like my 1995 base model came with 6 speakers (3.5" dash, 5.12" front doors, 6x9" rear), Neons have 6 speakers (3.5" dash, 6.5" front doors, 6"x9" rears) and my friends camaro's came with 6 as well (6.5" doors, 6.5" B-Pillar, 4"x6" in rear) so it's entirely possible to be stuck with 6 speakers and wonder how to hook up a 4-channel head unit to it. As suggested above, my friend (a camaro owner) used a 4 channel running off the rear pre-outs on the head unit, split them with RCA Y-connecters to get 4 signals, then ran the back 4 speakers off an amp to at least get somewhat of a fade effect. Most mulichannel amps should let you adjust the gain of the seperate pairs (the 4 channel I'm using in my Ranger does) enough that you can make the middle set quiet enough or the rear seat loud enough for a balanced sound from the driver's seat. It can seem a bit daunting, but in the end, it can sound great. The question is, does the van have lots of speakers now, or are you just trying to put in more? Older vans like the family 1986 Voyager we had when I was growing up just had dash speakers and rear liftgate speakers.