Life is so simple. Only money complicates it.**That** certainly seems to be true.
The Coincident loudspeaker concept (tending to higher impedance) that Israel has had for the last 10-15 years or so was developed using an OTL, not an SET. Unless you get a fairly powerful SET, I think you will find that in most rooms the Coincidents really are not efficient enough to bring out the best of such amps, although they are otherwise easy to drive- I find most of them need about 60 watts as a good minimum in most rooms (we've showed with Coincident a bit in the past at CES and had them in our shop so this is based on direct experience). We had one customer (also a reviewer) that ran one of the smaller Coincidents with our S-30, and while it sounded fine, she found that she was wanting more power.
We had a set of Coincident Total Victory loudspeakers here at our shop for several years; they sounded just fine but if I had to rate the efficiency I would say they were around 93 db.
We had a set of Audiokinesis loudspeakers here too; Duke of Audiokinesis rated them at 92 or 93 db 1 watt/1meter but they seemed more efficient than the Coincidents (Duke tends to be very conservative with his ratings; we've yet to see any of his speakers that didn't play well with our S-30).
We also had ZU Druids which were obviously more efficient (rated 101db which I think was a bit optimistic as well; 97db seems more accurate- otherwise also about 10 ohms) and also Classic Audio Loudspeakers which are 98db 1 watt/1meter (and 16 ohms).
So I have good reason to think the 93 db number I suggested above is pretty close.
In a nutshell, while Israel's amps sound just fine, on any of his speakers (unless you only play at lower volumes) I would think his amps won't make enough power although they do sound good together.