I've heard, and liked the duos with a number of different amps, such as the Art Audio PX-25 and the Viva Solista. I particularly like it with the Solista. I also heard the Duos with a couple of different OTL amps (one by S.A.P., the other a custom design) and liked the sound, but then again, I like OTLs. Generally speaking, I think this is an "easy" pair of speakers to match with amps because it just does not sound bad with a wide range of amps. This is probably because the bass is handled by its own dedicated amp.
To me, the weak point of these speakers is the bass, which is not totally integrated with the horns (sounds more sluggish than the horns) and also has a "one note" kind of emphasis in a particular range. Perhaps this kind of quality will be exacerbated by really "fast" and lean sounding amps, such as OTLs, but, I am personally not a bass freak, so I liked them with the OTLs.
I have not heard them with kit Audionotes, but I did hear them with the crazy expensive Gaku-On and a prototype Sogon. The warmer and "slower" Gaku-On sounded really good with the Duos, but I personally liked the leaner sounding Sogon even more. Again, these speakers are resolving enough that one can easily hear differences between amps, but unlike other revealing speakers, I never heard it sound really bad with any tube amp (I never heard it with high powered pentode amps, something I generally dislike).
