Just wanted to add Target have a great sale on at the mo on some of their car seats - I just got one today which was reduced by $100! Its a Safe n Sound Guardian convertable one, which is a recommend by the Roads and Traffic Authority, check out this leaflet which reviews a few different ones:
http://www.rta.nsw.gov.au/roadsafety...tockno4305.pdf

BTW I think the Target sale is only on for a few more days.