go see keith at cavern first, he should be able to at least point you in the direction of the parts you need if he doesn't already have them. Urbane has a nice selection of fixed-specific parts in stock, but they're a bigger shop with what some claim can be crusty attitude (i've never really experienced this). Both are deffinately worth a visit. Never been to Cogs, so i can't comment.
You might also want to visit Jet Fuel (again?) coffee on Parliament as it is a gathering place for all things bike-geekery. Hope you enjoy the visit.

EDIT: BTW - none of those shops are "rip-off artists". The only one of those in town is Igor on Queen west. do not under any circumstances buy anything from him as you will probably be purchasing something stolen.