Here is a lil rig to challenge rudi i think.
iPhone 4 > Bluetooth > MyST PORTADAC 1866 > HiFiMAN RE-400
Using the iPhone as it is a nice platform that also doubles up as my phone and of course has bluetooth. Then the portaDAC as it has a very high standard DAC and amp, much better than the iPhone has and does this via bluetooth so great flexibility. So why only the RE-400. Well i am really enjoying them but i am mainly using them as they are what i am currently reviewing so they make the rig and all in all, a very good one ;)