Hey, welcome fellow Calgarian! Nice to see another into good sounding car audio. Depending on what you have that you want to sell, you can try here actually. Kijjii can sometimes be good too. Hell, depending on what you have I might even be interested.
As for getting install stuff, I always suggest Mobile Solutions of Calgary in the SE (Barlow/Peagan) and Audio Concepts in the NE (32 Ave). They carry the best stuff and are good guys to deal with.