Excellent calculator example Murph! Power just isn't an issue in a small room. One thing the Crown calcualtor does not compensate for is room gain. Being in an enclosed space gets you another 6 db or so.
In my space, being at 8' from the speakers, I use between 2 and 6w including 12db headroom to get me to reference.
My room is small - about 1800 cubes. Maybe I'm just deaf.