Jupiter,

Assuming you have a pair of efficient speakers, you have more than enough loudness for 100 W RMS.

The volume of sound/music produced by a sound system does not depend on raw wattage, it also depends on the sensitivity of the speakers. If the sensitivity of a pair of speakers is at, say, 91dB/1W 1m. With 100 WRMS, its maximum loudness should be around 112dB (with twice the wattage, there is 3dB increase in loudness). However, if your pair of speakers' sensitivity is 85dB/1W 1m (most European made sweet sounding speakers are usually less efficient but more pleasing sounding), with 100 WRMS the maximum loudness is about 106dB, only one fourth the sound of the first pair of speakers. Most people are very comfortable using 1 to 2 Watts of power when listening to light music (around 90dB). I consider 100dB to be more than I can tolerate for music listening anyway. So you should not have problems with your 100 WRMS Hi-Fi setup at home for keyboard amplification if you set the volume knob to no more than 12 o'clock position to avoid accidental overloading.

Paul Ip
from Texas