Architects and building designers perform the same task when designing a house. Building designers are often more affordable, but often not as qualified (architects are members of a state regulated profession). However, regardless of whom you choose to design your home, it is ultimately up to structural engineers, your local council and your builder to make sure your home is constructed safely and soundly.
Then try using the region-specific search option shown above. This covers all the major regions and cities including Sydney, Brisbane, Perth, Adelaide, Melbourne and Canberra (ACT).