@jaymark good to know. A great position to be in, at least the speakers are good to go awaiting whatever amp you have to throw at it. I'm following along with your progress now, while helping a remote friend looking at some form of efficient [brand new] AMT based speakers. Maybe X5s for him. I do my own custom amt builds.
Sure seems like you are in the sweets spot for your X5s having both of these amps in your fleet. I can partially understand why, and would likely test the same as you.
Just wondering, since you already have the DS-65 tube amp, was there something which caused the need to try/go to the X150.5 instead, or did you already have that amp prior?