Once impedance is matched, the speakers' maximum wattage spec become a moot point, as long as they can handle your highest
chosen* playback volume, and that your receiver's got enough power for that, your good. Once you have an impedance match; the potential problems for wattage mismatch only arise if your not mindful of this fact.
Teenagers tend to ignore the signs and burn equipment, but most reasonable adults can live years with a Wattage mismatch without ever having any problems. The fact is, your system can be adequate as long as you don't over-stretch it. Keeping within the range of it's lowest limiting factor keeps you safe from any damage.
- If you push your kit with an underpowered receiver/amp: At certain volume quality will quickly degrade, bass disappears and distortion becomes very obvious.
Receiver/amp will burn out.
- If you push your kit with a receiver/amp which is too powerful: At a certain volume, speakers will distort sound, and tend to "knock" and "bang" on lows, and screech on highs.
Crossovers/caps can burn out, speakers and tweeters' coils may burn/weld or come unwound, and of course, Speakers can pop-out, tear at suspension ring or cones' edges.