.....the gauge is pretty much the inportant part...............you can contribute significantly to system impedance with very long runs of speaker wire whose gauge is too small......i use 11 gauge
all around & my two longest runs are 60 ft. There is also some discussion of the use of multistrand speaker wire with say 2 pairs of two insulated wires, each twisted....can aid in noise rejection. I use 4 strand cable ( 2 pairs of twisted 14 gauge, effective 11 gauge) on all runs.
Integra Research RDC-7.1, Bryston 9B-SST, NHT vt2, vs2 & sw2, Sony 65XBR10w, Moto 6416iii, PS3-250, Sony BDP-s550