Not sure this is what you are talking about Diki, but when I first got the Pa600 I thought it wasn't loud enough so I started adjusting the EQs ... then when I was playing some Big Band styles, and big Latin styles I was overloading the internal speakers like crazy and there were some harsh sounds coming from them ... I lowered the EQs and the internal speakers were fine ...
Yep... that's about it. Maybe the PA3X got the same styles as a reference point, but because it doesn't have built-in speakers, the distortion that the busiest styles might have if boosted is not the same issue?