All of my speakers are upgraded and I have to redo some things and I was wondering if I swap out the 6x9s to 6.5 with tweeters I would notice a difference in sound?? I have a jl 6 channel amp pushing the components and a jl 500/1 going to my sub..

 

No reason to put anything in the rear shelf if you have good speakers up front at all.

I wouldn't consider it a good investment of time, effort or money.

 

Well I have all polk components now and the fronts keep going out so I have some Boston pro series 6.5 just sitting in my closet.. I'm thinking of putting them in the doors and the panel next to the rear seats.. I guess I will just keep the 6x9 alone since I fade it to the fronts anyway.. It will be less work anyway.. Lol