Every car I have owned, the factory speakers have worn out, or were worn out when I bought the car. This results in an annoying buzzing/rattling noise and heavy distortion whenever the music contains any bass at all.
I prefer to use the factory stereo, and always replace an aftermarket stereo with a used factory unit, if the previous owner decided to install one. A typical factory stereo is rated for 20-30 watts per channel, which will support most aftermarket replacement speakers.
I like to buy 2-way or 3-way speakers, which cost between $40-50 before tax and/or shipping for a pair. I have found that these kind of speakers deliver the most bang for the buck, as they sound much better than a pair costing $25 with free shipping, but probably not quite as good as a $200 set.
For my 2000 Silverado, which only has speakers in the doors, I got a set of Insignia 4-way speakers, and a used GM AM/FM/CD stereo. For my 2002 Daewoo, which has 4 speakers, when I bought it, I replaced the aftermarket stereo with a used Daewoo AM/FM/CD/cassette stereo. Last year, I got a set of JVC Kenwood CS-DF620 speakers for the rear, when the factory rear speakers went bad. Now, the front speakers have gone bad, and after a lot of careful research, I just ordered a set of Cerwin-Vega H740 speakers to replace them.
I always try to attach the speakers firmly, using fine-pitched machine-thread screws, to avoid any potential loosening which would result in vibration. I always discard the wires which come with new speakers, which are 18 or 20-gauge stranded aluminum with spade connectors, and solder on a length of 18-gauge stranded copper wire to each terminal on the speakers prior to installation. Then, I use my T-stripper to cut off the factory plug, strip back the wires, and connect with wirenuts, using electrical tape to prevent any possible loosening.
I have had good results in every vehicle in which I have replaced the stereo and/or speakers. I would like to hear your thoughts and experiences relating to replacing a worn-out car stereo and/or speakers.