wiring 101:
the bigger the wire the better the signal, especially over long distances, the biggest gauge will be for your subs or woofers (yes, there is a difference between a subwoofer and a woofer) however your woofer wire shouldnt really be any longer than 3-4 feet IF that and depending on the wattage coming out of the amp, 10-8 gauge is a good wire. if you have like 2000 watts - go with 4-6 gauge
![Razz :P](./images/smilies/icon_razz.gif)
and some earplugs.
speakers like mid-bass and full-range dont really need anything larger than 10 - i usually use 12-10 depending on the wattage and the distance from the amps. tweeters are good with 14-16, since they are usually spliced from the mid-bass speaker and only have a few inches to go
power wires from your battery are VERY important to be gauged correctly - you can starve a system if you use too little of a wire - i usually go with the biggest i can fit - which is a 4-6, depending on how many amps i have, you can always throw another battery in the back with the amps - but you still have to use a pretty heavy gauge wire.
twisted wires are commonplace and basic construction for good speaker wire...
as far as speaker sizes - its been my experience (20 years worth) that anything bigger than a 12 is just compensation for a lacking in other areas. i've heard and seen 3 JBL 10s break windows in OTHER cars that 2 15's couldnt. i always stick with 10s - they can handle the low frequencies just as well as a 12 or 15, if tuned and powered properly. they take up less trunk space and dont require a lot of airspace to work.