Lornoah, I can't answer for the Xono, but the issue is the same for the Pass preamps. I the case of the preamps I spoke to Wayne at Pass Labs (I have the X1 with the smaller chassis PS). Wayne told me there is no performance or sound quality difference between the two style supplies.
The same PS is used for the Xono, but as this is a much higher gain signal amplifier I can't say if any slight variations in either style would be discernable.
The same PS is used for the Xono, but as this is a much higher gain signal amplifier I can't say if any slight variations in either style would be discernable.