Adrian,

As Jakewash mentioned, you'll be fine with 14-gauge. It doesn't affect fidelity. It does add a bit of resistance, so in effect you're wasting a teensy-weensy bit of power in the surround channel amplifiers in increased resistance.

I recommend 12-gauge to everyone to eliminate the aspect of any significant resistance in long runs--longer than about 30 feet.

Regards,

Alan Lofft,
Axiom Resident Expert (Retired)