Std fronts are 6x4's. Make some pods and put in 6" components.
I'd leave the rear speakers out of the parcel shelf to allow the subs to port into the car. Better sound, and reduction in rattling.
You can place rear speakers (if you have a coupe), in behind the side panels in the rear, ie the vertical piece of fabric above where your arm rests if you are in the back.
I made some pods for the void space behind the panel, removed the carpet, cut out a 6" hole to let the sound out, put a 6" speaker grill in there from Jaycar, and placed the carpet over the top. You would never know they were there, but you can hear them loud and clear.