There's nothing quite like the sweet sound of your favorite music coming clearly through your car's audio system. Unfortunately, the stock speakers in most older or inexpensive cars really are nothing quite like that. Unless you happen to get a new car with expensive factory audio upgrade, you're forced to listen to tinny, crackling distortions that drive any music lover nuts.
To get a complete stereo system upgrade worth paying for, you normally need to spend a few thousand dollars to replace everything from the head unit, the power wiring, speaker wires and speakers. And of course you would be adding aftermarket amplifiers, dj equipment rentals speaker enclosures and other accessories. That's a big project and a large bill to pay all at once.
There is some good news though. You can get a huge improvement in sound just by replacing the factory speakers that came with your car. The cheap speakers that come with most cars are made with the lowest quality material and construction methods to keep the costs down. You will typically find weak paper cones, poor wiring, and brittle glue holding it all together. These materials degrade quickly after much use since an audio speaker is really a moving part in your car, but the cheap ones are not very mechanically sound.
Even inexpensive aftermarket speakers will sound better than these. At the lowest end, an aftermarket speaker will have better quality cones, domes, and wiring. Paper may still be used in the cones and domes, but it will be treated and stiffened to provide better sound quality and more durability.
If you can spend a little more money, you can get into some more exotic materials such as carbon fiber or specially designed plastics. This type of speaker will give you even more range, durability, and have a higher threshold for power if you choose to add amplifiers to your system down the road.
Going up one more step, you can get speakers designed for stock speaker replacement that will have a special configuration that puts two speakers, typically a mid-range and tweeter, into the same space as a single speaker. And if you have a compatible vehicle, you can even get tweeter and mid-range speaker kits that have the tweeter in a separate enclosure for you place in an appropriate spot in your car.
It may seem like overkill to spend much money putting good speakers into your car without replacing the tuner or adding amps, but you will notice a big improvement with just this one change, and it paves the way to upgrading your system incrementally. By replacing the speakers first, you're able to enjoy better sound immediately while you take the time upgrade the rest of your system.