Ed,
I've heard the DeHavilland several times in a number of situations. They are well-built; Kara provides great service. I wanted to prefer the Aires to the Audion Black Shadow (the Black Night is a 300B PSET integrated) because Kara makes her amps here in the US, but that's not how it turned out. Nevertheless, the DeHavilland is a more affordable upper-tier option in SQ, and if it's the best amp you've owned you're doing very well. The more remarkable matter is how little coverage these 845 SET options get in the audio press, given that they put out enough single-ended power to put the vice grips to a far greater range of speakers than other SET designs built around less robust power triodes, and really sound beautiful and vivid doing it.
Phil