Most likely, if you have come this far, then you already know the basics about installing a speaker systems in your car. You may have already bought speakers, a subwoofer and a tweeter. If your wattage isn't matching up -- you have a slight problem. If you are looking to enhance your car stereo systems, then read on for some quick tips on buying car amplifiers.
* '''Calibrate speaker and amplifier power.''' If your amplifier is underpowered, when you increase volume, you will get distortion. If you have more power from your amplifier than you need, you may have wasted money, but that is generally not harmful (if you turn it up really loud you could ruin your speakers, but if played too loud even with a smaller amplifier that could happen too. Generally if you hear distortion, you might be near that limit.)
* '''RMS power''' is the best measure of amplifier power.
* '''Peak power''' is higher than RMS and is not terribly useful. It measures how well your amplifier will react to quick increases in volume, but often is just a marketing gimmick.
* '''Get an amplifier for the system you own.''' One speaker only needs a mono car amplifier, but if you have two speakers plus a subwoofer, you need to upgrade to a two-channel car amplifier. Anything from there and above, go for a four-channel amplifier. You will need it for a three or four speaker system, or if you have two subwoofers, to improve your volume overall.
* '''Location, location, location'''. Either in your trunk or under a seat -- make sure to keep it two feet away from your radio receiver to avoid any interference. Also, make sure that you install it where there is good ventilation so that it doesn't overheat. That means, not directly on the floor or wedged against a seat.
* '''Bass''' needs a low-pass filter for your subwoofer. Some come with one installed, others you may need to buy one separately.
* '''High frequencies''' need a crossover or high-pass filter for your tweeter. Either get an amplifier with it built-in or buy it separate.
* '''Speaker-level inputs''' are required when you've got a pre-installed stereo with a built-in amplifier.
* '''Preamp outputs''' are necessary when you are powering multiple speakers and subwoofers via two amplifiers.
* '''Simplify things'''. Get a remote control for mounting your amplifier in your trunk. Plus a voltage monitor to check that everything is working well. Or get a control center that can regulate the power sent to your various components so that nothing gets shorted out.
* '''Easy installation'''. Get a car wiring kit that comes complete with all the stuff you need for a painless installation process. You will get fuses and wires that you can get for the specific power amp you buy.