There are several options available when dealing with Amplifiers!
A Mono Amplifier is probably the type we sell the most of, due to the effect most people are trying to accomplish. These are most common if you are powering just a Subwoofer. Do you already have a Subwoofer and you just need to match it up? If this is the case we would need to know the RMS Watts and impedance on the Subs to properly complete your system.
2- Channel Amplifiers are great for Powering a pair of speakers, these have a great use in Vehicle with rear speakers or seats. For example a Regular Cab truck.
3-Channel Amplifiers are like having two Amplifiers in one. Generally you are able to run a Subwoofer as well as a set of speakers off these amps.
If you are looking for something versatile and capable of powering an entire speaker system in a vehicle look to a 4-Channel Amplifier. They are great for a basic system with front and rear speakers, where there is no sub-woofer. On the other hand they can also be used in a vehicle where no rear speakers are needed, but a sub-woofer is required. Most can be a 3-Channel or Higher Power 2 Channel .
When looking amplify front and rear speakers as well as run a Sub-woofer, a 5-Channel Amplifier may be the way to go for you. They are really 2 Amplifiers in One! They are very convenient especially in vehicles that have limited space. They can run 4 speakers and a sub-woofer!
6-Channel Amplifiers are usually used with a certain set up in mind. It is very similar to using a 4-Channel but with 2 additional channels. There are a lot of options for set up with them.
Let us know what you are trying to accomplish, and we can guide you in the right direction.