6x9s theres no such thing as a decent set there awful especially in a parcel shelf with a sub beneath it.
best set up you can have, nice sub in the boot amped, and decent components in the front amped end of no need for rear speakers ruins your sound stage.
If your really that concerned about passengers being able to hear the music, put in a cheap set of rear speakers sumwhere not in the parcel shelf tho.
And amp them also then put a switch in the remote lead for the rear speakers amp, so that you can turn them on and off as you please.