Car speakers vary greatly in cost, depending on the type of speaker as well as the quality. If your focus is on upgrading your current speakers, the cost is generally less. You can find good mid-range speakers in the $100 to $200 range. Higher-end speakers will cost closer to $300 to $500.
If you’re looking to ramp up the bass, you’re going to want a subwoofer. In general, the bigger the subwoofer is, the more you’re going to pay for it. You can pay as little as $60 for a 6-inch sub, all the way up into the $1000 range for subwoofers in the 15- to 18-inch size.
Keep in mind that if you want to maximize your sound, you’ll also want to ramp up the power with an amplifier. With a higher power output, amps can put out cleaner sound without having to strain to achieve it. Some speakers (and all subwoofers) require an amp to provide the power to run them. Expect to pay anywhere from $200 to $500 and up for a high-quality external amplifier.