So basically don't listen to them as loudly as an airplane taking off.as the guy who doesn't capitalize most stuff when he should, I find it particularly ironic that I get to point out the significance between mW and MW ^_^
now I've found somewhere 103dB/mW 27ohm, does that look like the IEM you're talking about? (they seem to have different versions so I'm not sure).
if those specs are correct, 20mW means pushing the IEM to 116dBSPL at 1kHz. and that remains true whether you're feeding the IEM from a balanced source or a single ended one. let's say you have a device with both single and balanced output. let's say the balanced output when set at the same volume has twice the voltage and OMG 4 times the power output!!! what all that is saying is that the IEM will have the music 6dB louder. P=voltage²/impedance twice the voltage is the same as 4 times the power and the IEM playing music 6dB louder. into that same load(the IEM) all those stuff are really saying the same and being the same. so once you've plugged the IEM into the balanced output with your super duper balanced cable, the music in this example is going to be 6dB louder than your usual preferred level, so what do you? you turn down the volume by about 6dB and 'magic!' the IEM is now consuming 4 times less power again. you won't send more power without knowing, if it's not louder, it's the same power, and the dangerous level here(again if my specs are the right ones), is when you listen to music with peaks at 116dB. I don't know for you, but I don't do that too often, or ever.