The fact that you find little difference between LOD and HO on SE530s on an ipod classic, yet a lot of difference with UM3X is a little strange. The classic's internal amp is poor, you should see a difference if you are using decent quality IEMs (like the SE530's) and a decent amp (which you are using). To then go on and say that the UM3X exhibits a lot of difference is again strange, given how most people have heard no difference when amping the UM3X (I in fact DBT'd).
I've tried the UM3X through high end sources, and adding an amp to the chain has made no difference, an experience that a lot of other members will relate to. But you might well hear differently - I would be very cautious in recommending an amp as an upgrade for UM3X unless your source is poor.
