From what I've read, the XA25 is both underrated and that class A has enough more current to be plenty of power...I think. The 30's push a little harder even, I think. I'm not sure and hope some with direct experience can speak to that.
I'm surprised with the Leben, too. It's a wonderful piece of gear that I hate to see go and I'm definitely having some seller's remorse. It may be a mismatch with the DAC, but I think the 2V (not mV!) output is pretty standard. I'd have to find a DAC with a higher output or sell the Tannoy and neither seemed too viable....
I've looked at the Audio Mirror Tubadour SE, but the output is the same. Lampizator has some models with a 6V high output switch.
In the end, starting with the speakers and finding the right amp makes the most sense. Maybe there's a higher output DAC that would make good music with the Leben/Tannoy but in the meantime, I'm hoping a Pass Labs amp with a Supratek pre will make some beautiful music.
From looking around, the 30.5 seems a little rounder than the .8 with the 25 being the warmest of the three. Hopefully, someone's tried one or more of them with some tannoy Stirlings or Turnberrys (Turnberries?) and can weigh in.