Fred, obviously situations vary, but at a comfortably loud average listening level with speakers of average sensitivity at a typical listening location about 1 watt is used. Much more can be used on brief peaks, depending on the dynamic range of the material being played. A frequently suggested rule of thumb to allow for peaks on material of very wide dynamic range is to provide for 20dB higher than the average listening level. 20dB higher than 1 watt would require 100 watts. Some material(e.g. some almost uniformly loud pop material)is dynamically compressed and requires far less in the way of maximum power capacity. For example, it can be noted that the distortion audibility tests that Axiom conducted some time ago used pop material with a dynamic range of only about +/- 5dB, for simplicity.
An "all channels driven" power rating isn't realistic for home use and speakers never simultaneously have to use full power on program material. The typical 2-channels driven rating required as a minimum by the FTC amplifier regulations and used on most units is more in line with reality.
The Yamaha 659 which you mention should indeed have sufficient power in the vast majority of setups and would be an excellent choice if the features are suitable. Incidentally, don't fall into the trap of using irrelevant analogies relating to cars or anything else. This is the sort of argument that those pushing high-priced stuff sometimes resort to, because they have no justification in audio terms.
