Thanks! I've had Belles Aria monoblocks, AVA M225 monoblocks, and the AGD Tempo all plugged into the Puritan at different times, and in all combinations there was the same improvement over without the PSM156. Nothing more powerful. I really don't believe the Puritan is current-limiting. There are one or two long threads about it over on AudioCircle--you might find users there with the kind of amp you're curious about.
Great system! I'm a fellow owner of TWL and Audio Envy cables and former owner of Harbeth! Curious, did you ever try a more current-hungry amp with your Puritan PSM156? Trying to figure out if the PSM156 limits current delivery to bigger amps. Can't find specs anywhere!
The M225's are very good. They are little powerhouses. Given their topology, I wouldn't necessarily choose them for speakers with very low impedances, but then the Harbeths are above average in that regard. They get out of the way. The comments on them over on AudioCircle tend to wax very lyrical; I'm not sure I would go that far, but they let the rest of the components shine and don't hold them back in any way. And--a bonus--you don't need an engine hoist to move them around, the way you do with many 225W amps!
Congratulations sir!! Finally got to see your new setup. And are you kidding me? You got the Rhumba too. How do you like it? I absolutely LOVE mine. What tunes have you tried on this? If you can, get the Psvanes - these are killer tubes. I have read reviews that these ever better some NOS.