Let's not confuse the differences between the needs of electrostatic loudspeakers and those of planar magnetic speakers.
Electrostatic speakers are voltage driven. They require amps capable of swinging large amounts of voltage. As frequency rises the amount of voltage needed declines a bit. Amps that have problems with ESL speakers have trouble with the load of the speaker. ESLs are basically capacitors. This is also why ESL speakers need different speaker cables than other speaker types. Current is not an issue.
Planar magnetic speakers are current driven. They are resistors. Many are easy loads for amplifiers. Of course some have been designed with one ohm loads, and then become problematic.
Steve