It happened to be I having both stereo bluetooth unit too. In fact I still having Moto S705 and i.Tech 803 before.
Yes Sony MW600 tend to have higher output, but it's also still exhibiting Sony typical V-shape, rough and Hi-Fi sound.
To me pairing Samsung HS3000 with Samsung Galaxy S3/Note2, the default Music Player provide are much better sounding than any 3rd party player under default Nomral EQ setting both on the cellphone and the bluetooth unit. They are by far the most cleanness, livelier and better sounds separation MP3 playback I've heard so far, when side-by-side comparing to Motorola S705, Sony MW600 with the my TDK-200 IEM, and I've remebered i.Tech 803 with Sony MDR-EX500SL did not sounded this good too.
The much better sounding I've think most probably was because the S3/Note2 default Music Player was streaming the audio with aptX codec. Switching to any other 3rd party music players, they did not sounded as clean and livelier. And of course aptX not necessary mean better sound, but in HS3000 case it is.
My impression of Sony stereo BT unit, as with my older Sony MW600, it just sounded so rough when side-by-side comparison to Samsung HS3000. Even i.Tech MC803 and Motorola S705 sounded cleaner than MW600. Maybe I put it this way, my impression about Sony BT was they always sounded too Hi-Fi to me as I've always prefer better musical sounding device.
Btw, even though HS3000 output was around 3dB lower than Sony MW600, but it is still loud enough most of the with time, even with low volume CD directly rip to MP3 or FLAC without boosting volume by 150%.