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

Tboooe, I think all your assumptions are right and your conclusion regarding the need for power is right - we generally need a lot less than we think. I would only argue that given the same basic design approach, the lower power version of that design will sound better at a given volume level if the amp has enough power to reach that volume level with a given speaker. In the case of the 250.5 versus 350.5 comparison, the more powerful amp may sound better in this case if it is a no negative feedback design and the lower power amp isn't.

Thank you for the calculation, but it's pretty obvious that theory does not match reality.

As to the whole thread it does not seem that there is agreement either. The punch line actually reads 350W is preferred over 250W, yet 200W is as good as it's going to get (assuming the doubling of power for a 4-ohm). To be exact, even 120W is plenty. This does not, I think, help the originator of this thread or myself. The whole discussion is strictly about Pass Labs. So to make sense out of the power vs performance question, design differences between these amplifiers of the same designer must be pretty drastic. It's too bad that Pass Lab does not have enough dealers for a convenient audition. By default, I begin to lean more and more toward Ayre MXR by the week.

The design differences between and the X.5 and XA.5 are quite "drastic". And pure Class A watts are not the same as A/B watts - in part because there is more to power and sound levels than just watts. By the way, Ayre is also first-class SS amplification - can't wrong with them either.

With all that being said, I would still recommend the XA60.5 or the XA100.5 depending on budget and need for the pure clase A sound versus the A/B. With the Wilsons, again because they go down to 4 ohms I recommended the XA.5 series b/c they can double power. There are times when the ability for an amplifier to provide more power can be significantly appreciated. Even though by the calculation the needed watts to acheive a spl are low, having more watts does offer more headroom and this comes across as control and dynamic differences. Thus the recc for the XA.5s that double down.

The X series also doubles power, always has. But the XA is a better sounding design if sufficient power. The XA100.5 is wat more than enough power with the Revels for 99.99% of the time is most rooms.