i use a Sansa Clip Zip, rockbox'd, and it sounds better than any smart phone i have heard [iphone/flagship to mid tier android phones].
i have also had the good fortune of pairing it with a Fiio Amp[dont remember the exact model] and listening through the ATH M50 and A700.
it was an experience unlike anything..
- - - Updated - - -
also, it can play 24bit 192khz flac records without any lag. its another topic that 24bit-192khz is overkill and not needed. but the capability of the tiny player to play files of such high resolution without any lags is just tremendous.
the phones that i have tried generally transcode the flac to play them. and iphone does not support flac
and 15hrs of music playback capability = major win.
- - - Updated - - -
oh.. there is ALAC for Apple.