Your comments /experience are a good example of quality compared to quantity in regard to amplifier power. The 700 watt Nord was not the sonic equal of your much lower power tube amplifiers (With your speakers). No surprise to me.
If the Pass Labs XA 25 is a ’close’ 2nd to two superb tube SET amplifiers that’s quite a compliment indeed for the XA 25. This is a pure class A (25 w at 8 ohm/50 wat 4 ohm class A) relatively simple circuit well designed amplifier. I suspect it would be better sounding than the often praised Parasound amplifier matched with the Tekton Encores. I’m certain I’d love the Encores driven by the 15 watts from the Allnic given my listening preferences. And yes the EML XL 300b is an excellent tube both in sound quality and reliability.