I am using 14/4 CL3 speaker cable. It is 14 ga high strand speaker cable, 4 conductors. It is all in one jacket, about 10mm in dia. I bought it from www.mcminone.com
I can give you a part number when I get home, it was 33$ for 100ft. Actually, I'll have about 75 ft extra when I'm done that I could sell you cheap if you want it.