Nick, the first point is that the Crown calculator certainly isn't a "great calculator" when a home listening room is the venue. It's based on an anechoic measurement without the room reinforcement that changes the measurement significantly. The result from using the calculator unadjusted for the room is as much as 4 times the true number. Crown fails to even mention this key factor on the calculator page and only brings it to light here
near the end under "Other Considerations" where it suggests adding 6dB for the room contribution, which is equivalent to reducing the power figure to 1/4th of the previous value shown on the calculator.
Also, as was pointed out previously, but you apparently can't accept, the only way you can "feed" a speaker more power is to make it louder; simply connecting an amplifier with a higher maximum output rating does nothing. If a speaker such as the M80 is using about 1 watt for a comfortably loud average level, 1 watt is all that it's being fed, regardless of whether the amplifier can output a max of 10 watts, 100 watts or 1000 watts.
Simply keeping the volume control on a receiver or separate pre-pro at the same number doesn't keep the volume the same when a separate amplifier is connected. The separate amplifier can have a different gain than the amplifier in the receiver and can be slightly louder at the same volume setting. This is why blind listening tests have to make careful adjustments so that the volume is matched within 0.1dB for the units under test. Louder gives an impression of being better, rather than just louder.