Look closely at the power of your radio. Usually it is specified in the documentation or directly on the device. Remember that here you need a nominal and not maximum power, which often has high value, which is a kind of advertising course manufacturer.
Then decide to power speakers, which must be not less than the nominal power of at least one channel of the amp. The optimal value is such that in 2-3 times exceeds the power of radio. After the appearance of the stock, the sound will have minimal distortion, and the lifetime of the column will increase substantially.
Pay special attention to the sensitivity of the speakers, which allows you to give it a more loud sound. Don't forget to read the resistance value of the load receiver, after choosing the dynamics need to consider this option. To achieve maximum power it is necessary that the resistance was not less than the minimum value specified on the radio. To reduce the resultant resistance can connect the speakers parallel to each other.
Think about where you want to install speakersin the door trim or back panel of the trunk. Depending on this, decide on the number, size and manufacturer of the speakers. Remember that not always a large number of them will affect the sound quality.
Also look at the manufacturers, who have long been engaged in production of this equipment, because here you are less likely to buy a defective product. An important factor is the cost of a set of columns, because often that is what is crucial. Don't forget the design and color of installed equipment, which will delight your eyes and ears for a long time.