You could run all the power requirements for 2 houses on 8 guage wire!. 16 is the normal minimual 14 is kinda the above any system requirements and 12 is even way overkill for just about any system. Even 14 is isn't compatable with lots of inwall volume controls, etc. Most of them will only take up to a 16 guage. Stick with a high strand count wire. We normally wire all houses with 16 guage 65 strand wire. We only Use 14 when when requested, or for higher end systems.