An 80-watt amp is more powerful that a 5 Watt one. Well yes and no. Watts ratings are a rough guide. What is more important is usable power. An amp with much higher rated power may not be usable if after the first few watts its situates in distortion the other problem is power handling under load.
An amp has to respond to the varying loads that speakers cause as they reproduce different parts of the musical spectrum. A poorly designed amp may loose control under demanding notes, particularly the bass spectrum. What is the point of more power when you are just putting out one note bass.
The power rating of an amp may be used as an selection criteria as to whether an amp is considered or not. This may a practical concern as to lower power may not drive the speakers selected properly. Yet more power does not automatically make one amp superior to another. Solid state amps, at least the ones I have heard tend to have a similar behaviour once they are turned up the music hardens up so the full capacity of these amps are not always usable either.
