Chris, you really can't "overpower" a decent speaker. You're far more likely to damage it with clipping from less power.
And just because an amp CAN put out gobs of power, doesn't mean a speaker will draw anything different than it currently is, unless you play it a lot louder.
Either way, it's not like you're really out of the range. If your speaker were rated for 50 watts and you hooked it up to a 500 watt monoblock, then yeah, you could damage it if you actually ran that power through the speaker.
In other words, you'll be fine!
