16ga, no issues, works great with my AR3a speakers. I can crank those buggers louder than I can stand without a problem. Unless you go long distances, over 20' or so, I wouldn't sweat it. No issues with quality either. Try for yourself, use 18ga, then switch to 16ga and see if you can tell the difference. Likely not. That experiment is cheaper than buying some expensive stuff and never knowing it it sounds any better.