Buds91RX7Conv

I picked up a 91 convertible a few weeks back and have been working on a little of this and that to get it where I can drive it and have a little fun. My next project is getting the stereo sytem working. At the moment I have an occasional left channel and about half of the headrest speakers sort of work. Enough I guess to let me know the switches in the center work.
I have looked around on here and found a couple of good threads on the headrest speaker replacement. But the other info seems a little scarce. I even tried Critchfield but the specs they give for speakers doesn't seem to match what I have.
I have a set of speakers in the doors at the very bottom forward corner that should be the original stock. Those should be 5 1/4 or 6 1/4" I believe (dont have the info sitting here) The ones I am not sure about are the pair that are in the lower protion of the wall behind the seats.
I know there are a pair of amps that i have seen one of while going thru the car. I have seen the one behind the driver's seat that is for the headrest? I think.
Ultimately I would prefer to try to keep the head unit and just do speaker replacement, but the left channel that only seems to fire occasionally i fear may be in the head unit. I therefore may replace the head unit as well. What I really am focused on is trying to keep the headrest speakers and center controls since it is a unique feature of these vehicles.

Any suggestions or information about the stereo setup with an aftermarket stereo or even just the right speaker replacements would be greatly appreciated!!