We took our new Aspect to our stereo guy before our first camping trip, and we did go a little over the top. He put 4 4x9 speakers in the coach part and component speakers in the front (separate tweeters). You really need good speakers up front in the "van" area. You cannot hear the coach speakers while driving unless you really crank them.
Also, to get good sound, you need to use an amp to power the speakers. Amps are not just for high volume, you need them to give good full sound at low volume too, otherwise it sounds sharp.
There are lots of good small car audio shops around, most can set you up with something afordable that will suit your needs. If you are looking here for advice on what to do, you obviously don't know enough. Spend a few bucks and get it done right.