@richdirector Maybe the Arden/s 93dB sensitivity/20wpc minimum reco vs. 91dB/30wpc holds the answer there. The Leben is 32wpc class a/b while the Luxman in class a has much more current. I don't have any experience with class a power beyond the first few watts in Plinius integrated and an SA201 I had years back - hardly relevant!....I can only call 'em as I hear 'em.
There seems to be some evidence around that 25wpc in Class A would do the trick with the Stirlings, too.