Quote from your link: "For example, if you need 100 watts continuous power to achieve the desired average SPL, you need 1,000 watts continuous to handle 10 dB peaks, 3,162 watts to handle 15 dB peaks,..."
So, for 15 dB peaks over average SPL we need
31,62 times more power. OK.
Now quote from my post #18:
For average SPL = 92.5 dB/1m it needs average 11.2 W.
11.2W x
31.62 = 354 W needed for clean 15 dB peaks. Or as I wrote: "400 W allows clean 15.5 dB peaks".
Q.E.D.
Another quote from your link:
Total amplifier power required in various applications
- Nearfield monitoring: 25 W for 85 dB SPL average (with 15 dB peaks), 250 W for 95 dB SPL average (with 15 dB peaks)
- Home stereo: 150 W for 85 dB SPL average (with 15 dB peaks), 1,500 W for 95 dB SPL average (with 15 dB peaks)"