This is not meant to step on anyone's toes, and definitely not those of the OP either, but I do find it amusing sometimes when threads like this pop up, when speaker wire is so cheap to begin with.
For instance, here is a 50 ft roll of 12 AWG for
$11.82.
I just recently read that with extremely long runs, resistance is not really an issue (since you can buy thicker gauge) but it's the inductance and/or capacitance that might affect freq response, and I guess some amps don't like high capacitance either.
However, I'm guessing that the above represents some insane runs representing a lot of wire mass; nothing you would ever see in a typical home.