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

You will get better sound. I the case of Pass Labs .5 amplifiers, the X350.5 is regarded the best among the stereo amps. Something magic is present with the X350.5 but it will come at a cost. The sheer mass of the construction is maybe the answer to you tweaking guys out there. The power you are using for your cuddling moments with Elvis or miss Krall is subtle, never exceding double digits. The obvious difference between the amps is power rating but since most playing is only a fraction of the rated power actually used, the answer has to be somewhere hidden from ordinary wisdom.

>Having gone from 200 to 300 watts with both Levinson and Pass amps, driving fairly inefficient speakers, I can confirm that more power is better.<

That might be true for your speakers/amplifier, but in this case there will be no difference.

Well, being a dealer I can A/B them. I have and this is what I see: Deeper bass, hard to believe but there is way more control, seemingly endless EFFORTLESS power, more transparent (hard to believe), more open on the top and sweeter sounding. Basically, you get more of everything. If you like the Pass sound you will get more of it

Fatcataudio, what speakers did you use for your evaluation?

Proac's and AAD 7001's.