That is not an accurate statement for all cars. I personally ran a pioneer unit connected to the bose amps, and the sound was fine. I had a little crackle when the volume was down, but that rarely happened. My brothers 87 is wired the same way, with a JVC unit. You do not have to rewire the car to run new speakers, or to put an aftermarket CD player in. If the speakers didn't work before, most cases this means the amplifiers have gone bad. Another thing you have to look for when you bypass the amps and hook directly to the speakers is the impedance of the speaker. A normal speaker is around 8 ohms. The bose speaker, when I measure mine were 3 ohms. I believe most aftermarket head units are set up for the 8 ohm speakers. They may or may not work fine, I would imagine they would work, but would have a limited life span.