Hi all - I am currently a FIIO E7 owner fancying an upgrade. Somewhere under 200 quid and I'd like to plug it into my Samsung Galaxy S4, my Nexus 7 and occasionally my laptop or desktop. Headphones of choice are normally my Westone 4Rs or a pair of Audio Technica ATH-ES7s. Have been quite happy with what I get from the E7 but just fancy heading a step up. I'd like it to be driven by its own power (Not AC or from the device), be a headphone amp and USB DAC. Any advice? I looked at the Fiio E18 but not sure how much of an upgrade it offers.