Allan Loft wrote what I think is the best article around describing power requirements. Easy to read for the dummies in the room (self). One watt is just fine for background noise, but for those of us who prefer things a bit louder, 100 watts becomes the minimum, not the max. http://www.axiomaudio.com/power.html

And his follow up article on head room description and power requirements. http://www.axiomaudio.com/dynamicheadroom.html

People preaching power needs should really understand these basic principles and make clarification to what they are talking about when they tell others that they “only need” a few watts of power.