For a wagon the biggest difference would probably be the cargo area. There are cheaper alternatives to Dynamat if you search around for suggestions. Also look at the wheel wells and under the carpet. The doors are a given but the cargo area will make a big difference. Don't forget the spare wheel well.
Tint all windows that are legal in your area with something that'll block as much UV as possible, add foam and silicone to the clips holding the front trim piece on the dash that meets the windscreen, and add felt or rubber to the surfaces in the ash tray and glove box to silence the stuff in them.
In the back, put velcro on the cover for the spare to keep it in place or it will make noises as it moves about. Search scoobymods for the rear fog light mod. Wire footwell lights to work with the dome lamps. Add interior/exterior thermometers.