Any business dealing with Protac, Altech or Synnex.
These are all wholesalers, so any retailer selling ASUS, Chaintech, Ge Cube, Sparkle, Galaxy, XpertVision, Leadtek, Gigabyte, MSI, Inno3D, or eVGA, AND who buy these brands from Protac, Altech or Synnex should have good support from their wholesaler, but whether they themselves offer good customer support as a retailer, I cannot say.
I recently returned a Sparkle card to Protac that died within 20 minutes (very uncommon for this brand). Sent it back on a Wednesday, they received it Friday, and I received a replacement Monday. Excellent service from Protac at a wholesale level.
All three have very quick delivery at wholesale. For retail, you'd best ask who they purchase a particular brand from, that way you'll know if they have the backing of a wholesale-only company within Australia, or they import their own.
Apologies for the half-answer.