Don't buy monster cable. Although they make a decent product, it's not worth the extra money they charge to cover their uge advertising budget.
The gauge of wire you need is dependent upon both the length of the wire, and the Ohm-rating of the speaker. How far away from your amp/receiver are your speakers going to be?
This page has a handy chart that tells you the minimum gauge required to carry the full signal over a given distance for a given load (ohm-rating). For example, since your M60s are 8-ohm speakers, you can safely use 18-gauge wire up to 30 feet. Most people like to err on the side of caution and step up to 16 or 14-guage though.
I'd recommend buying regular "zip wire" in at MOST 14-guage for your entire setup. (12-gauge is pretty thick and can be hard to work with.) Home Depot carries this wire in bulk and will cut to length. Alternatively, you can order a 100' spool of 14-gauge Sound Kind wire for about $35
from here.
As far as your subwoofer is concerned, you won't need speaker wire for it. To connect it to your receiver, you will need a coaxial cable with RCA connectors.
Something like this will be perfect, and at a great price!
