Dude, why not just use a headphone amp? Even just a tiny one. I haven't used an an-amped phone on it's own as a DAP since I was like 12. Then I discovered PMPs and got my first job to fund a purchase (an Archos Juke Box and paper round respectively, lol). Now decent dedicated PMPs (reasonably priced, not the dx100!) seem to be getting phased out with convergence devices so I'll get an Android phone when my Cowon D3 (also Android) becomes unusable. However I'd have no qualms about using a small headphone amp. Then again, I mainly use portable audio when studying, hiking and doing DIY/chores so I'm perfectly fine carrying a combination (note 2 + slim amp) which is still significantly lighter and thinner than the walkmen/discmen which people used as their portable source for over a decade.
Efficient (low impedance) cans help too of course, so that a bulky amp isn't needed. Using an Android app to remap the keys and add media playback function to the few tactile buttons on the Note 2/S3 helps as well so you don't need to be pulling it out of the pocket to switch tracks or pause playback.
Can you point me to the app that remaps the buttons?