helotaxi-thats good info for speaker wires, but I think he wanted to know about the sub wiring. Correct me if I'm wrong. For subs, it depends on what your running and what kind of power you'll be feeding your sub. I'd go for the 1/0 size wire for the power and grounds.
Just wanted to stop in and introduce myself. I'm Ryan from NC and I look forward to gaining more CA knowledge from you guys. Seems like a lot of you know what you're talking about when it comes to car audio and hopefully I'll learn a trick or two.