There are some carbon fiber sleeves that work reasonably well for your speaker cables. The carbon really eats up that rf energy. Do a search for them online, several places have them for sale in various sizes.
At one time I found some 16awg coax for sale and I used that, tying the shield to the amp chassis and using two coax's for the speaker. That did kill a noisy CB radio from a nearby neighbor, too. Unfortunately, my daughter snagged them for her stereo (fortunately for her!)
The best thing for speaker cables vs. power cables is distance. Keep them at least a foot or more away and you won't have any interaction. The line level audio cables are, or should be, shielded, so they are less of a problem. Still, I wouldn't route them too close to power cables. You can slide the coax line level cables inside them, too, which will help if you have rf problems.