See each headphone has certain impedance(opposition to flow of current in lay man terms), any source has to force ample amount of current through the electromagnetic coil of headphone.
As the impedance rises the job of producing natural sound & delivering required power gets tougher on part of the source ( mobile, pmp...).
In my observation, generally all current mobile phones easily drive IEM's up to 24 ohm impedance.
My moto G is unable to drive my 32ohm IEM's (they get loud but don't reproduce what the laptop does, since laptop has greater power supply capacity).
Considering the fact that, your IEM's are 40 ohm ones, you must look source with ability to drive those.
IMO, for mobility you can look for Fiio X3 type players or if you are comfortable, youcan simply buy a cheaper external AMP for laptop...
