Does anyone have a recommendation for a good quality replacement for the 6in. harmon/Kardon speakers in the rear door? mine are blown and I want to make sure I go back with something that is going to sound good, at least as good as factory.

 

Those are stock Rover speakers, the only thing that is H.K. on your truck is the amp.
As for what speaker to use, that is your call, go down to Best Buy listen and buy what sounds good to you.