Let me share my findings:
Monsignor's Barber Shop
109 Featherston St
Huge selection of midrange razors, many soaps, creams, brushes etc. Good choice of rare DE blades. All in all very nice place, run by a lady of strong opinions & character. Very expensive, but it is to be expected in this part of the world...
Smith & Caughey in Queen St in the City:
Full Tabac Range, including the pretty hard to find jar of soap. They sell the local Goodfella razors as well. Apparently there'll be a sale in two weeks' time.
On Pitt St, just before K Rd.
They seem to have a lot of cheap razors and kind of "beginner's" gear. Interesting shop.
Please add to this thread, it'd be good to get an overview!