I put my front speakers at the bottom of each door.  The rear speakers
were same size replacements as the factory speakers which are located at
the same spot as your rear AC.  My Westy doesn't have AC.  This works
quite well acoustically.  The amp was mounted behind the passenger front
seat on the back of the battery box.  A wood board was screwed onto the
metal.  The amp is screwed onto the wood board.  This keeps the power
lines short.  Coming off of the amp is a long line for the subwoofer box
which is not attached to anything.  Not only can I quickly remove the
box from the van, but I can also move it around.  Normally it sits
behind the amp.  I tried a 10" and it didn't seem to have a full sound,
so I went with the 12" sub.  The sub box also serves as an extra seat.
The only bad thing is that the middle seat is not really usable
simultaneously with the sub box, but I rarely have the middle seat in.

Opinion for Tracey - Go to your local stereo shop to have them install a
new amp.  It will be the best 50 bucks you ever spent.

As an added comment for everybody else, when buying a new head unit,
look for one that has a line input.  This is useful for MP3 Discmans
and/or laptops (MP3s and DVDs).  My sub box also serves as an excellent
place for my laptop when watching DVDs.  It sounds close enough to
surround sound for me and the sub box is amazing as well.  On my trip to
Mardi Gras this year, my passengers enjoyed using my laptop as an MP3
jukebox.

Dana

85 Westy
dshowers@cpds.net