The amount of power needed for your home-theater receiver depends, in part, on the speakers you choose. Given a certain amount of power, different speakers have different sensitivities, a measure of how loud they are.
The standard measure for speakers' sensitivity is how many decibels the speakers produce with 1 watt of power at 1 meter’s distance from the speaker. A more sensitive speaker requires less amplification to reach the same volume level.
Keep the following factors in mind when deciding how much receiver power you need:
Consider the size of your home theater and how loudly you plan on playing your movies and music. If you want to create permanent hearing loss or have a room the size of the Taj Mahal, you might need a receiver that can pump out 150 watts per channel.
If you have relatively sensitive speakers and a moderately sized home theater, and you don’t plan on testing the thickness of your window glass with really loud music, a receiver with 70 watts per channel (or less) might do the trick.
In general, receivers with about 100 watts per channel (accurately measured) are more than powerful enough in just about any home theater.
Amplifiers (whether separate or in a receiver) make their power by using transistors. In the old days, amplifiers used vacuum tubes — and some really expensive high-end amps still use tubes because some audio enthusiasts prefer their sound.
Inexpensive receivers use an IC (integrated circuit), which provides the power-generating transistors for several audio channels on a single chip. Better receivers have discrete amplifier output transistors — separate transistors for each channel. Typically, you get more power and better sound from a discrete design.
