well, considering I just went to 3 shops today and non of them had what I was looking for, I thought I'd see where everyone gets their PC parts from.
personally, I use the following:

Computers only - great online store with decent prices. had a small issue with them "not receiving payment notification" but otherwise a good supplier.

matrix - the usual store I go to in Springfield Park, Durban. they have a good variety and decent pricing. caters more to business needs now than gaming though.

PC Zone - usually when I go looking for something, it'll be here. specific components have worked hundreds, but I've heard that their PC setups can be a bit shaky. however they seem to be outsourcing them recently so I think standards on that front have gotten a heck of a lot better. the one I usually visit is the pinetown branch.