Boom, welcome. First, if you look at the auditioning thread you'll note that SeanF is listed in Edmonton. You might send him a PM.
On surround positioning, although you've used the term "rear channel", I assume that you're actually referring to the side surround speakers in a 5.1 setup rather than back speakers in 7.1. The position of those speakers depends on where you'll be sitting. They should be on the side walls about 3' above ear level and in the absence of back speakers should be slightly farther(maybe 2')back than the listening position to lend a little "back" effect.
The size of the wire would depend mainly on the length of the run and 16ga would be fine in the majority of cases.For a good explanation of speaker wire in general by a veteran audio professional together with a table of suggested gauges see
this .
