Here is what my setup was like (pre theft):
   JVC KD-SX990 receiver
   Front Doors: Pioneer TS-A1057 4" 2-way speakers
   Rear Shelf Speakers: Disconnected
   Rear Box Speakers : two el-crapo 10" "pickup style" boxes, which I
placed in
     front of the rear bench seat.

Pros:
1. Cheap
2. The rear box speakers were not mounted permanently and had an
extra 20' of wire, so at a campsite, you can just pull them out of
the van and set them up outside.
3. No amp required, efficient use of battery when engine off.
4. The JVC has an IR remote, which I velcro to the wall in the back
of the van, for use while in bed.

Cons:
1. Sound quality : the box speakers were $30 each, and I got what I
paid for.
2. Theft magnet:  the box speakers Looked like they cost $300 each,
and someone broke in and stole them.
3. Putting the box speakers in front of the bench seat blocks the
rear heater.

So I'm wondering if perhaps a higher quality set of box speakers
would make this an even better setup?    A friend suggested I just
drape a mexican blanket over the bench while parked to hide the
speakers, which seems like a decent idea to reduce the theft
temptation.  I'm in California, so I don't really mind if the rear
heater is blocked.

Any opinions on these:  http://www.amazon.com/gp/product/B000068UXA