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

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

Proac's and AAD 7001's.

There is a difference in the design, the X350.5 use no negative feedback in the circuit. It also runs pure class A to 50 watts versus the 30 of the 250.5.

Spatine, I would go with a pair of the new XA.5 series as they double power as the ohms half. This may not be an issue, but since the Wilsons look like they are 4 ohms you would be doubling power, so in my book it would be a nice benefit if needed to get the XA.5 series. I would suggest the XA60.5 or the XA100.5. I don't think the added power of the XA160 is needed. please let me know if I can help at all.

The XA.5 series DO double down in power. The XA series do not. There was a mild re-design to allow the doubling of power. It is sonically insignificant, but if you want or need more power on tap the doubling down is a bonus.

Let's let Taboooe do the calcs for your power requirements. As for the amp size, I never recommended the X350.5 over the X250.5 or anything else, I just chimed in and said it sounded better to my ears for the reasons I listed. I believe the XA60.5 or XA100.5 would do just as well and offer things the regular series do not such as righer midrange, more liquid highs. At the end of the day, do you want pure class A or hybrid A-A/B?

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.