Regarding pre-outs, the Yamaha spec is 1V RMS...
Some people complain this is too low.. what they don't understand is when mating an AVR to a component amplifier. Component power amplifiers have
different input sensitivities depending upon where built and application. If the power amplifier was designed/built in the Orient for consumer applications its sensitivity was typically 1V. However if designed/built in the USA for pro-audio applications its input sensitivity was higher like 1.4V RMS. So now one can easily see if the pre-outs are only 1V it will have difficulty in driving an amplifier with a 1.4V input sensitivity to rated output....
Frequently a pro-audio amplifier has
more output power and is less expensive than a consumer amplifier so they are frequently used in consumer home theater applications mated with an AVR. So now one can easily understand why the complaint of limited power, is a result of
mismatched components...
The workaround is
before purchasing an amplifier double check its input sensitivity specs, note that many of the pro-audio amplifiers have
switchable input sensitivity of 1V or 1.4V..
Just my $0.02...