Measurements don't tell you how a piece of gear is going to sound, no matter what brand, especially not measurements from REW
Sure they do- but for that simple reason you rarely see them , and I've found that many people don't understand what the measurements are saying. The things to look at are distortion vs frequency (must not rise across the band or the equipment will sound bright), distortion spectra at 1 watt and at all frequencies, distortion spectra at -6dB of full power, and IMD (not CCIR version), the latter at -6dB of full power.
Interpreting this information properly will tell you exactly how the amplifier will sound.
100 dBs SPL is painfully loud.
If this is the case it points to a distortion problem causing the pain, unless you have hyperacusis.