Tony, I wonder if the maximum voltage output of the 665 is actually 1 volt. What's the source of that spec? Be that as it may, power is proportional to the square of the voltage(Ohm's Law), so if both those numbers(1.7 volts and 1 volt)are actually accurate, the relative maximum power outputs would be in the ratio of 1(squared)to 1.7(squared)or 1 to 2.89. The output with 1 volt input would be about 35% of the output with 1.7 volts.
As to a "good match", any good amplifier which is transparent works well. There's no sonic coloration produced by the amplification which would be harmful.
