Another useful trick to run speaker cabling through walls is to use CAT5 ethernet cable. It's very resistant to noise and is low resistance.

Strip both ends.
You'll have 4 pairs of conductors.
Each pair has a solid and a "striped" conductor.
At each end, untwist the pairs a couple of inches.
Connect the "solids" for one channel.
Connect the "stripes" for the other channel.
I usually put cardas banana plugs on the ends.

For all but the highest current requirements, I'd put this up against almost any affordable speaker cable out there. I used to bi-wire my Dahlquist DQ-20i's to my Adcom GFA-5802 this way and my buddies who were spending thousands on MIT Oracle cables thought they sounded VERY transparent.

Cheers,