well as far as things like Turbos, BOV's, WG, etc go... most people and shops buy their items from the same place. JRP.
Intercoolers and such I'd say ebay.. I know a few people who've ordered them off there and used them.. they actually look like quality pieces and you're saving a ton of money.
Obviously turbo's can be found from other places... Such as Cherry Turbos in St. Catharines (really nice guy to talk to, very knowledgeable), Turbo Masters (Mississauga) and a few others.
One place that I can't recommend at all would be monster-turbo.com/J&R Fabrication... although they've now merged with another company in Scarborough somewhere. Not sure what they're called. But there are much better places to buy a turbo from believe me.
If you're asking for specifics about what turbo would be best for your build, well that's a completely different story and that involves a lot more planning and information.