if they use the amp at high volume, most likely the IEM or more accurately the drivers will be damaged but that will take quite a long period of time. The amp wouldn't be damaged, if it cannot put out the current required, all you will get is clipping on the SQ.

a common use of impedance adapters is to remove ground loops (hissing) that you get when the gain of the amplifier is too high and the impedance of the IEM is too low.

right, thanks for clearing that up!

OT: any first impressions of your JDS cMoy?

i can't wait for you to try it out too!