Honestly, my plan when I finally buy my 5.1 system is to get some QED micro cable. I will then be putting a few clips in place to hold it to the corners of the room where I intend to run it, and then painting said cables and clips the same colour as the room.
As I see it, I then have the cable I want which will hopefully have minimum impact on the room in general as it will be painted to match the walls. I may be missing something here, but could you not get the cable you've got your heart set on, then paint it black (hence the Rolling Stones reference)? I understand you wanting to get some black cables, but would this not be an easier solution?