The advantage of an OTL on this speaker is due to the very high impedance the speaker has in the bass. This peak is not due to resonance. Solid state amps will throttle back their power into this impedance and so getting the speaker to play bass with solid state is problematic.
OTLs OTOH can make power easily into this higher impedance, which works well with the electrostatic characteristic. A lot of our customers have commented that with our amps they don't need subs to make convincing bass.
ESLs in general do not obey the same design rules that box speakers do. Most box speakers are designed around the idea of being 'voltage driven' which is to say that the amp driving them can act as a 'voltage source'; being able to make the same voltage regardless of the load impedance. ESLs work better with an amp that makes constant power with respect to load impedance. For that you need a tube amp with no feedback so its output impedance is high enough for this to occur (you can also do this if voltage and current feedback in the amplifier are done in equal amounts, but this is very rare in amplifiers!).
For more on this topic see:
http://www.atma-sphere.com/en/resources-paradigms-in-amplifier-design.html