Thanks, Musiclover.
I'm no expert on EMI/RFI. However, my general understanding is that the longer a run of unshielded interconnects gets the more likely it is you will pick up noise. At 3m, there is a good chance you would be able to get away with unshielded cables without introducing any problems. As I mentioned above, I am running a 6m pair of Morrow MA3s with absolutely no noise pickup.
My suggestion is that you call Mike Morrow to talk with him about his shielded and unshielded options and to get his recommendation for your application. You can always try Mike's cables at no risk for a 60-day audition and return them for a full refund if you encounter problems.
Morrow Audio Cables