[NZtechfreak]

I've owned both the US and International S3, the Wolfson-bearing International model sounds better. The volume output of the International S3 is a bit low, however if you Root the device you can install audio tweaks to fix that (note: these tweaks are NOT Voodoo, Voodoo is NOT available for the Galaxy S3, these are adaptations of the old Voodoo tweak).
 
Having said all of that, both S3s are capable of using USB DAC/amps on stock software via USB OTG, so if you really want to improve the quality you have that option also. In the portable sources forum there is a thread "USB audio and Android devices" (or something like that) with information on that, including all DACs confirmed working with the S3.

 

[Pruikki]

what did you mean, i have Xperia S, it has USB otg support.
 
is there a dac i can just plug in trough it? 
tell me more, i suddenly have some money to spend on it!

 

[Crypticmx]

Yeah, I have the Samsung Galaxy S, which is rooted with Voodoo Sound. What Voodoo sound does is bypasses the firmware, making full use of the Wolfson chip within.
The sound on that exceeds the S3's sound, and goes much louder.
Still waiting for a Voodoo Sound update for the S3, but I'm personally happy with the sound. It doesn't sound so different as to ruin the experience for me.
 
I am looking to buy a DAC/AMP though.

Try the Boeffla kernel on your S3, i never heard the Galaxy S with voodoo sound, but people say that boeffla sound does as much for the S3 (if not more), as voodoo sound did for the original galaxy S.

 

[Pruikki]

Rooted My S3 4g lte GALAXY and now have Boeffla mod 3 stable release
 
its great!
 
Rom manager will install CWM with no fuss and make backup of rom in case fail at something.
 
Easy to root S3...such a Dev device.