Actually, that would work fine at low volumes. Watts RMS average. It may peak at 80 to 100 Watts, but the average RMS output is far lower than you'd think. But you don't get something for nothing. Let's face it, a race car goes faster than a passenger car because it has a ton more power.
Same idea works for speakers.
Well, as stated earlier, your home stereo may only average 10 Watts RMS, but on loud passages in the music, it may peak to its full 100 Watt potential. These peaks may only last fractions of a second but without that reserve power, the sound of your music would suffer terribly. . Headroom is the reason you may see a sound engineer running an amp that seems much too powerful for the speakers. What that person failed to realize was that by badly mismatching his amp and speakers, he ended up pushing the power amp so hard that it was constantly clipping. You can't really under-power a speaker as long as the power is clean.