My Denon has a "rated" output of 1.2V. By rated, I assume Denon means maximum. And I assume that's RMS.
In a perfect world, all manufacturers would adhere to the standard line-level preamp and AV preamp output levels in order to ensure compatibility between different components. However, I can tell you from my days bench-testing gear for a Canadian AV magazine, that so-called "standard" output levels varied all over the place. I sometimes measured preamp outputs as high as 7 or 8 volts, which would overload the input section of any amplifier.
It would be interesting to actually measure a Denon or Integra's preamp output levels when Audyssey is operating. . .