A lot of people use Japanese Stax amps outside of Japan. Some of the older Stax amps can easily be converted to accept different voltages by means of a voltage selector (in the form of a jumper block) on the back. Newer amps however do not have this ability, and need to be used with a step-down transformer. Alternatively, it is possible to open up the amp and reconnect the wires from the transformer for your targeted voltage, but this is difficult and requires soldering. In case of the smaller amps (SRM-212, 252 etc.) that use an external power brick, you can buy a new suitable power brick for the correct input voltage.
Thanks Michgelsen, this is helpful and reassuring. I was thinking of another solution, driving the STAX headphones through a Lyr + Wee combo--does this make sense? It comes to about the same price, and I'd have some versatility with the Lyr to drive non-electrostatic phones. Thanks in advance for your thoughts.