I have the "snap" ferrites on everything coming out of the PC.... USB keyboard and mouse, DVI, usb to the SDRIQ, if its a cable coming out of the pc it has one! I try to keep mine close to the pc, and I wind as many turns of the cable as I can fit thru the opening. Power cables---choke those as well.
I also have them on coaxial cables as they enter the house.
My noise floor is quite low here, despite Two PCs in the room, and several RF generating devices in other parts of the house.
In my case, I could watch noise blobs fade out as I added these things.