Unless you peg the volume at reference levels for extended periods of time, you'll be fine. Keep in mind that a lot of that power is in the bass range and that's all going to be diverted to the sub by your 990. Also, overdriving a speaker with a nice crisp signal isn't *nearly* as bad as driving it within spec by an amp that's overextended and starting to distort.

In short, I wouldn't worry about it. The extra power comes in handy for dynamic music/movies and is unlikely to harm your speakers.

I can't imagine cranking it way up with the Klipsch speakers in any event as they're a bit shrill to begin with. They do have the advantage of being quite efficient though.

Cheers,