As I compared before, the sound with DAC+AMP (ODAC+Headstage Arrow 3G) was much more dynamic and better soundstage (more deep+wide), also much more silent the background (low noise).
After I switched back to SGS3 direct, I can confirm phone has enough power to drive my IEMs, but I always felt boring and dull, closed sounding.
And it seems the phone also makes sometimes small noises which an be easily heard when music is quiet.