Hi my name is Movin On, and I've been working in the field of car audio and mobile electronics for 8 over years. I've installed everything from navigation systems to full car stereo systems, remote starters, alarms, and beyond. To learn more, visit our web site at www.movinon.com.
No matter what type of car audio system you have, you have an amplifier. Even your factory stereo has a small amplifier built into it to power all the speakers in your car. If you are looking to upgrade your car stereo and power your speakers, you are probably going to need a 4-channel amp. A 4-channel amp has 4 outputs - one for each speaker. Usually these outputs are more powerful than a factory amp and can drive high-end speakers. A 4-channel amp can typically give anywhere from 50 to 100 and higher watts per speaker. But really, it is going to depend on what type of speaker you are powering.
If you are powering subwoofers with your amplifier only, you are going to need a mono amplifier. Typically, a mono amplifier can drive 1, 2, or even 3 subwoofers depending on how they are wired. A mono amplifier is typically designed specifically to power subwoofers and to be crossed over at a low frequency. They are usually high power and high efficiency.
If you have a complete car stereo system with 4 speakers and a subwoofer, you may want a multi-channel amplifier. A multi-channel amplifier has 4 outputs - one for each speaker, and has a single output for 1 or 2 subwoofers. Typically, multi-channel amplifiers are not extremely powerful, but in most cases they can power any car stereo system. If you have an unusually large car stereo system with high wattage, you may want to consider getting a separate amplifier for your speakers and a separate amplifier for your subwoofers.