I have a very low level hiss to mine as well but it's there regardless of their gain settings and only noticeable if I'm right next to the speaker. I have them connected to my iMac via optical and my Benchmark via balanced. I usually just set their volume to the midpoint indent and use the Benchmark's volume from there. I definitely don't notice it when playing music and I'm not that concerned really as they sound fine when playing music at all levels.
Bill