Hello again, Don, long time no hear. It's hard to say exactly what may be the cause of the difference in sound that you hear and it may have nothing to do with the relative power output capabilities of those two units. As far as the Yamaha goes, you can be confident that it actually would provide the advertised 75 watts per channel(with the standard 2-channels driven measurement), otherwise it'd be in violation of the FTC power rating regulation that all amplifiers sold in the U.S have to meet. Those are continuous power ratings and one feature of some NAD amplifiers is that they provide a much higher output for a split second to meet peak demands, so it might actually have a higher peak output than the Yamaha. But again, power output might not be the factor in what you're hearing.
Now for more interesting stuff, I recall your special interest in chamber music and I'm reminded that a few days ago in the Water Cooler section Mike Drew had asked for a recommendation of ten classical recordings, which were given him. His response to them indicated that he especially liked the string music, so I made additional suggestions that included my two favorite chamber works CDs. You might be interested in the two discs that I suggested there containing the Debussy, Ravel, Dvorak, Borodin and Tchaikovsky string quartets.
