A:Answer Hi Steve,
The DHT-S316 is an active device - in so much as it is a speaker with it's own proprietary amplifier built-in. Wattage ratings are only of any use when looking at which amplifiers might be compatible with any given speaker pair. The amplifier used for the speaker within the DHT-S316 was designed specifically to bring out the best in it.
If a speaker is very sensitive, it may only need 3 or 4 watts to go very loud. If a speaker is insensitive, it might need 50 and 80 watts to go very loud.
The reason we do not include the wattage rating here is because it doesn't really tell anybody anything if the speaker and the amplifier have already been correctly matched for performance and power. Optimum performance at realistic listening levels can be achieved with any amount of power depending on how demanding the speaker might prove to be.