You'll find receivers, stereos and amplifiers with all kinds of different power ratings. Mostly displayed in number of WATTS.
Now, there's 2 kinds of ways to measure how many WATTS your equipment has. In PEAK and in RMS.
Another way to put it simply: Eight "AA" batteries combined produces 12 volts. And so does a standard car battery. But eight "AA" batteries WILL NOT turn over your motor. The car battery has more AMPS. And AMPS are more important than WATTS.