After a lot of research around here and abroad, it looks like the E17's might be best? But this is a last resort to get any possible meaningful, factual support for this or any other brand of portable headphone amp.
Look into a Cmoy amp from JDS Labs only like 60 bucks USD. or if you want to stretch it to a bigger price, the C5 from them.
Both of those are good.... while your looking at JDS you might consider the O2 also...