I have a set of the in dash tweeters that was part of a six speaker system in pre 97 XJ's. Do they really add anything? I have the door speakers as well as the rear cargo area sound bar.

 

Pictures would help, even though I know what they are and where they go. Speaker technology has come a long way, and yours might have not aged well. New speakers would probably be a better investment, and use the stock wiring.

Or you could do what I did and have a set of full size dash and door speakers, with a switch to choose between them. That way, when I have the doors off, I still have speakers. However, make sure to use a proper 12V switch (like a DPDT rocker switch) and to not switch them while the radio is on. I blew the driver speaker output on a radio, and had to get a new one. (Yes, it was the radio, not the speakers or wiring. New radio plugged in and all speakers work fine).

Same story for the soundbar, newer speakers would probably improve if the speakers that came with it are worn. Look on the forum, as there are many different solutions to wiring them up on the pre-97 XJs