you can use whatever kind of wire you want for speaker wire pretty much.
For a while I was using 2awg power cable from my amp to my subs, it was all I had. Didn't sound too good but worked fine.
Big thick wire for speakers is only good up to a certain point, past there the internal resistance of the wire itself starts to mess with you. Electrically, its fine, but acoustically it ain't too good.
If you need to do a long run (100 foot +) go to a good stereo place, they will have tons of advice to give you. They have special types of cable for really long runs. If you are over 250 foot you get to use those cool +17v convertors
