I have an e-power and the 14650 battery in it has a bit of trouble supplying a dual-coil with enough power...
Right off the charger, when it's running at 4.2v, it does an okay job.. But I'm suspecting there's MAJOR voltage sag (This could be confirmed with an in-line voltage meter, i don't have one though) because performance isn't all that great.
You could try it with a 14500 IMR, should fair better.. The thing is the max discharge rate of the 14650 is 1.5C, they are 1050mAh so let's say 1.5A max discharge, after this it's abusing the battery/going to give major voltage sag.
Powering a 1.6ohm dual coil needs a current draw of around 2.3 Amps... the battery simply cannot handle it. It might be OKAY for some people right off the charger, but my 2.0ohm boge spin circles around dual-coils for me, and I'm pretty sure it's because a sole 14650 battery cannot handle it.
You can make a 14500 fit in the epower, by stretching the spring. You could try AW IMR 14500s (I have some on teh way, but haven't tried it), or you could go with a box-mod with enough power to push through these things... without using IMRs you'd more than likely need an 18650 mod, or 14500 in parallel mod
--An 18650 e-power would probably have the juice to push them with the right battery...