Not to be contrary, but I've found that if I overpower the chit out of my speakers, I've never had an issue. I ran a Klipsch RF7 pair biamped with two 1.0t mkIIs for years (SERIOUS overkill), then Kappa 9s with the same mkII pair - and I listen LOUD. However, at the merest hint of distortion, I back off (what's the point of listening to distorted music??).
I am a firm believer that as long as you don't exceed the mechanical limits of your speakers, you will have an exceedingly difficult time killing them with too much power. On the other hand, too little power - another story all together;-)