TL;DR The headphone jack isn't long for the phone world. Consider a DAP or external USB DAC/Amp, and keep in mind the issues with Android and USB audio.
Motorola dropped the headphone jack earlier this year, and the suggestion is that the new HTC will do the same in October. With Apple having done the same on the new phones, it's reasonable to expect Samsung will follow suit in time.
That leaves three options, buy a phone with a headphone jack and keep it running as long as possible, use a DAP or go down the external DAC/Amp Route.
Because I don't want to carry and charge another device, my solution is an iPhone, Lightning to USB adapter, Audioquest Dragonfly Red and a rubber band. If I need to charge and listen, I use the Lightning to USB adapter with Lightning pass through.
I mention this because in this scenario an iPhone may be the better choice today. It seems that the forums dedicated to head-fi are reporting issues with Android and external DACs. Both Chord; Mojo, and Audioquest; Dragonfly have posted information on these issues, which eminate from recent Android versions that don't natively support audio out via USB.