One must be very careful with longer runs of any cable. Cables will, in some capacity, act as an antenna, and pick up all sorts of interference (EMI, RF, and otherwise) along the way. The cleanest solution is to use balanced cables. However, if you’re considering such a long run of single-ended cables, I just wouldn’t. Also keep in mind that a quality 10ft cable is likely to be very expensive.
What are the EMF sources you’re trying to avoid? Are you confident they’re actually causing issues?
My audio equip. is sitting directly under 3 24" monitors and about 10 inches above my office PC. I can tell that the music gets smoother when I turn off the monitors. My amp is also sitting just under a monitor. SO I’m looking to make a change. What do you think of just extending my optical ethernet run - that would move all the equipment well away.
I don’t think you could hear or measure interference with a balanced/XLR cable. You’d likely not hear or measure any differences with shielded RCA cables either. While headphone cable runs tend to be only 1’ to 3’ long, home stereo and home theater routinely have to cross a room and travel near problem areas. Pro Audio people run cables many, many yards to wire a theater or arena and XLR was invented as the pro solution.
If standard XLR or shielded RCA didn’t work, I’d be prone to create a metal EM shield between the cables and interference sources. This might involve running the cables through a U channel or square tube under the monitors.
But, I’m not a high-end cable proponent and personally buy $20 to $50 Worlds Best Cables myself. Mogami is Mogami, Canare is Canare, etc.
You should be fine using a long Mogami XLR cable. 3 meter is a touch on the long side, but MAY work. It may not either. Tracing and killing e-gremlins involves a lot of trial and error. Some of the tracing may come down to IC and power cord positioning.
Understanding this may not be possible or practical for everyone, I keep an audio rack next to my desk (rather than having my gear on my desk), thus theoretically avoiding such issues. My important equipment is not sharing (nearby) physical space, electrical connections, or data connections with my desktop equipment. It’s a magnificently quiet setup.
@andris It looks like you are the recommended 3 feet from sources. Looks nice and yet still handy
Any cable discussion brings to mind a t-shirt I saw Lachlan Fennen (the Passion for Sound guy) wear for 1 of his reviews, which made me laugh! 
Yeah, I saw that review! Love this t-shirt. 
I’ll put my 2 cents in for the Kimber Kable Hero. Wonderful sounding interconnects, surprisingly better than the BetterCables SilverSerpent. Alternatively I don’t think you’d go wrong with similarly priced offerings from AudioQuest as well. Kimber and AudioQuest would be my go to’s.
