Late to this thread. I’ve owned the Nines and now the 0/96. I’ve heard many of the amps mentioned here and owned several too, including the Air Tight and more recently the Leben 600x. The Leben is a terrific amp, and the 600x is essentially many amps rolled into one, as it supports at least 8 tube configurations. I’ve been happy with KT77s, and most recently experimented with 6L6 variants. The Leben is very neutral and takes on the tone of the power tubes used. Want warmth and SET like presence - try the TungSol 5781a. Want more dynamics - try the Gold Lion KT77. Want a more sparkly top end and solid bass - try the 6550. But absolutely swap out the stock line stage tubes for some NOS versions.
I’ve also tried a number of 300b amps and they are magic on the O/96. Depending on the quality of the transformers and coupling caps, you can get classic SET magic, or even robust bass as well. I’m keeping the Leben but I’ve got a second setup using a Bottlehead 300b pre amp with Vcaps, coupled with a custom built Bottlehead 300b amp using vintage nickel transformers and exotic Mundorf silver foil oil capacitors. 8wpc and it will outcompete a number of big ticket competitors.
Off the shelf, my vote is Leben 600x, AirTight ATM300 or 211, I’ve liked the LM and LTA amps, and while Shindo is nice I find their sonic signature a tad dry for my ears.
I have not tried a Class A solid state amp with the Devore but have eyed a First Watt. Accuphase also seems interesting, as do certain of the Luxman integrateds.
The O/96 does not need very much power but the quality of the transformers (not their weight) along with the caps and resistors can make the difference between typical gooey midrange and polite extremes, and wonderfully defined bass, clear musical highs, and that eerily “in the room” presence that only a SET can bring.
Let us know what you end up with.