Absolute silence when no signal is present is a laudable goal, but not an absolutely necessary goal. I have not found a direct correlation between system performance and the presence or absence of a faint hiss emanating from speakers. The presence of the hiss is directly influenced by the amp/speaker combination; i.e. take the identical rig and remove a higher efficiency speaker, and put in a less efficient speaker and the hiss diminishes substantially.
When I was younger and newer to audiophilia this was an IMPORTANT thing to me. Now, with a more seasoned perspective it is relatively unimportant (Note clearly that I am NOT saying noise in general, especially noise is perceived to impugn the sound quality, is unimportant).
If you have to put your ear to it, it's not a serious issue, imo. This is very common. Many audiophiles with hearing loss or noisier rooms have this and don't even realize it. I suspect the description that the noise is gone when the music starts is not true. (I'm NOT suggesting someone is a liar or foolish) I believe it is due to the presence of the signal noise and music that the very faint hiss is hidden. Even in silent passages of music such a his is exceptionally difficult to isolate. If there is a perception that the hiss is gone when playing music, that is your answer; it's not a deal breaker.
selman, I hesitate to give an example mentioning actual components, though I have built hundreds of discrete rigs and encounter this regularly. I will not mention actual components because there is a form of delirium in Audiophilia wherein people react reflexively to anything perceived as potentially negative. I'll not subject perfectly fine manufacturers to such ignorant reactions.
Simply trust what you are told about it not being a major issue, and that it can occur in many, many situations. If you hate it and must have absolute silence, change your components. It's that simple. BTW, I may be wrong on this, but unless the noise oscillates it would not be radio frequency noise. I suspect that would be very unlikely. :)