Something does not compute. 40 amps into an 8 ohm load is not 500w it is 12,800w. And to get 12.8Kw out of an amp you would need to put no less that 12.8 Kw into it. At 120 VAC that would equate to 105 amps into each monoblock, or 210 amps to run a stereo pair. I don't know too many residential homes that have that much service coming into the house period.
This is what happens when you let the marketing people write the spec sheets instead of the engineers. That amp might be able to put out a millisecond length burst that approached 40 amps if it could pull from large bank of power supply caps, but that is very different from saying the amp can produce 40 amps. Sorry, but from the point of view of an engineer that is that is just disingenuous. And I am not talking about so for repeating it, but rather the sales people who put BS numbers like that out in the market.