My take on this is a good pair of earphones will enhance your listening experience, irregardless of player. A high bit rate or higher quality music file will also gives you that extra fidelity, that will otherwise be lost when you compress the music too much.
When I used to commute by buses and trains, my portable gear consist of a iPod -> line out dock (cable) -> headphone amp -> earphone. Music files are either 320kb/s or Apple Lossless. This gave me my ideal sound quality (within my budget).
Now that I drive, a portable gear is no longer as necessary. So now I just simply use my Note 2 and a good pair of earphone on occasion when I need to immerse myself in music and remain portable. Of course the music files remain high bit rate or lossless. To me it is quite sufficient and gives pretty good sound quality.
In case you are interested, I am using UE TF10 now. If I want more bass, I'll switch over to my UE SF5EB (EOL already). Another thing I find is that different music player apps does have some difference in SQ. Currently I am using Poweramp (which is one of the few Android apps that supports Apple Lossless), which I find sounds better than the stock music player. And keep any equalizer or sound effects off. This sorts of degrades the SQ.
But if good sound quality is the ultimate aim, even at the expense of being pocketable, then you'll need to look at the whole chain. From the player to the cables to the amplification to the earphone. And also the quality of the music file. Thats another poisonous road that will need deeper pockets..... :devil: