I have owned the iRoc for about a year. I used to own a Wavelenghth Brick and Cosecant (non-async version) as well as the Bel Canto DAC 3 and the iRoc blows them all away. I recently upgraded my iRoc to the new MusicStream and have logged about 20 hours of listening.
As is the case with most audio gear, the MusicStream probably isn't twice as good as the iRoc. I'm hearing instruments and vocals that I haven't heard before in recordings that I've listened to hundreds of times. I'm attributing most of this to an improved soundstage. This is saying a lot as the iRoc has an impressive soundstage. The MusicStream and iRoc share similar sonic characteristics which is a good thing as the Ultra Fi USB DACs are much more dynamic than other USB DACs that I've owned or heard that tend to be flat and lifeless.
In summary, if you can afford the MusicStream, then IMHO this is the current king of the USB DACs. If you're on a tighter budget, then I'm confident that the iRoc will not disappoint.
As is the case with most audio gear, the MusicStream probably isn't twice as good as the iRoc. I'm hearing instruments and vocals that I haven't heard before in recordings that I've listened to hundreds of times. I'm attributing most of this to an improved soundstage. This is saying a lot as the iRoc has an impressive soundstage. The MusicStream and iRoc share similar sonic characteristics which is a good thing as the Ultra Fi USB DACs are much more dynamic than other USB DACs that I've owned or heard that tend to be flat and lifeless.
In summary, if you can afford the MusicStream, then IMHO this is the current king of the USB DACs. If you're on a tighter budget, then I'm confident that the iRoc will not disappoint.