Audio Upgrade
I have been doing car audio for a long time, and I have installed many C3 stereo systems. I like to keep things simple yet extremely effective.
Start off with a modern head unit. You can easily modify the gauge bezel to accept the mounting cage for the new head unit. I can recommend some head units if you can tell me some of the features you are looking for.
Next, speakers. I recommend FRONT ONLY. Rear speakers will muck up how your brain perceives the sound in a cabin this small. The front speakers, usually coaxials are best, can be mounted in the kick panels easily.
Now, it's best to amp the front speakers. I also recommend a small 2 channel amp mounted in the passenger storage compartment to power the front speakers.
Finally, and not everyone is into bass, but a sub can be added in the back, in a small sealed enclosure, that still leaves room for the T-tops. I have done this a lot, and I have one in mine as we speak. The only other main difference is it adds to the total cost, and you'll need a larger amp to power the sub AND front speakers, and it would best be mounted on the back wall.
A member here named Wuttin installed a system guided by my recipe and it turned out awesome. Search his threads and you'll see lots of pics he posted of his install. He spent a lot of extra money on things like sound deadening material and high quality stuff but it's very achievable.
I will post images of the installs in my '77 and my friend's '74 but your car has a different rear compartment than our cars.
As mentioned, I can design you a system perfect for your C3 that fits your budget. Just tell me what steps you are willing to take as far as cutting your bezel and kick panels for modern head unit and speakers.


I then wanted deeper bass, so I did this

I would not buy a head unit form a catolog. you can get a nice head unit at Best Buy or Circuit for under 100.00 It just depends how many bells and whistles you are looking for.
Buy a new Bezel from one of the catologs and keep the original.










