Hi psjl,
The answer sounds like a classic Ayre answer. One, it's forthright and adamant (I said hostile but it's not - just convinced) and two, they're right.
Here is the info from the Japanese distributor of Ayre's products. You'll see the spec sheet and 750W (the max power draw rating). The unit uses two transformers per chassis.
I am not an electrical engineer nor a designer and Charles knows what he is doing. That being said, the transformer capacity is rated at 25% above his max RMS load (600W vs 750VA). Don't know how many joules his capacitors store. Some supplies are crazy overkill but from my survey, most high end units strive for 33% or 50% larger than the max work load.
Also if you click on the pdf link on the following page for the MX-R, a brochure pops up, still in Japanese, with the specs and "750W(MAX)".
Ayre Lineup