From Pass X250,5 to 350,5 : what to expect?

Hi
I am planning on going up from my 250,5 to 350,5 but first decided to ask if it is worth it.Are there any sonic benefits in upgrading to a more powerful amp in a ,5 line?As far as i know in the previous line (250,350)going up meant actually downgrading sound because 250 amp was sonically superior to 350 one.I do not really need more power but i heard that 350,5 is way better soundwise than 250,5.Is that true?Thanks for your insights on this matter.