Put some 6.5s components or coax's in the door by making or buying a 4x6 to 6.5 template. You can add tweeters to the foam door panel near where it curves meets the dash. Put a 10" or a 12" sub in the trunk/hatch and you're gtg.... Ditch the rear 4x6 speaks if it's a hatch, or do 6.5s in the rear deck if it's a coupe. Whatever brand you like, I like Alpines myself but what you decide on depends on your budget.
