Check the references. They're not pulling numbers out of their ass.Amplifier manufacturers guidelines are hardly honest.This is what crown provides as guidelines:
The designer of my speakers often used Spectron power amps at shows.
You also need to factor in the use of DSP in the equation.
You can do all the calculations you want, but in the end what matters to me is the real world experience in my room. And for the levels I listen at, the amps I employ fit the bill.
Mains: Yamaha P7000S
Center: Adcom 7705 (1 channel)
Surrounds: Onkyo 3009 Receiver
2 18" subs: iNuke 6000DSP
1 18" sub: plate amp