Rrog, do you mean you are surprised that I recommended one of our used amps rather than a new one? Its true that I avoid direct recommendation of our products, even when I think the recommendation is warranted. However ESLs together with OTLs have a history that goes back to the very first ESLs. In this case the desire was for a monoblock balanced tube amplifier to work on an ESL...
BTW a good number of older/smaller ARC amps benefit from the use of ZEROs as well. I've seen that with ARC and ESLs a number of times.
ESLs for the most part are driven better by tubes if their impedance is manageable for the tube amp. Its seems to me that a number of ESL manufacturers are trying to increase their market share by reducing the impedance of their speakers, to make them work better with transistors. The problem here is that transistors will sound bright on ESLs, due to the difference in impedance from the highs to the lows, which can result in as much as a 5x or 6x difference in power! So IMO ESL manufacturers that take this tack are shooting themselves in the foot by cutting off the technology (tubes) that works best with their speakers.
for more information see
http://www.atma-sphere.com/papers/paradigm_paper2.html