That's why I never like the term "power", ie "watts". Electromagnetic speakers are really voltage sensitive device, not power so if the R700 produces about 88 dB/2.83V/m, if you sit 4 m, you get only 76 dB assuming no room gain.
That's probably what you listen to a lot of times, but that means peaks could be at 96 dB or higher, fast approaching "reference" level!
Then consider Ohm's law, during impedance dips to 5 ohms, current will increase 1.6 times and that's what the AVR would be sensing, not "watts" whatsoever. At the higher, or highest current demand, the so called "watts" the amplifier has to supply is not that easy to estimate, it could be lower or higher than one thinks, the important thing is, the amplifier has to be able to meet the current demand while distortions remain lower enough to be audible.