OK, so Cindy from digizoid got back to me (this late in the evening too!). Hopefully she can help me get it tuned down as you have suggested. I figure that once I'm able to reach lower volumes, the hiss will also go down as well.
First, make sure no wireless devices are near the ZO2. RF signals can mess with the amp and cause hiss. This could explain why others have not reported the same thing with the same setup. Also, the quality of your files may matter quite a lot.
If those things dont help, contact digizoid about getting it adjusted and let the bliss continue