Welcome
I needed a second car seat and came across this model. According to Google's cache it was $249 on 2 June. It's now less than half that, and the cheapest convertible car seat I could find. Delivery is $15, but pickup is free (you need to wait for them to ship it to your local branch first).
Reviews are alright (average, nothing that stands out, comparable to other car seats). It is compliant with the 2010 standard.
Description from Site
The Hipod Senator with sound converts from a forward-facing car seat with in-built harness to a booster seat and is suitable from 6 months to 6-8 years (approx). It features luxurious cushioning and shoulder pads for superior comfort, contoured side wings for valuable side impact protection and in-built speakers compatible with MP3 players. Includes an adjustable headrest and a machine washable cover.
CREP Rating: 3/5
CREP safety ratings from http://www.crep.com.au/crep-results.php:
Restraint's Crash Protection Performance in
Minimising forward head displacement (critical feature) 16/16
Minimising forward knee displacement 6/8
Retaining the dummy's head in frontal and side impacts 3/12
Retaining the dummy's torso in frontal and side impacts (critical feature) 12/12
Maintaining its structural integrity in frontal and side impacts (critical feature) 12/12
Ensuring the harness buckle is still working properly after front impact (critical feature) 4/4
Managing impact energy to the dummy's head in frontal impact 4/8
Managing impact energy to the dummy's head in side impacts 0/8
Managing impact energy to the dummy's torso in frontal impact 4/6
Minimising upward movements during rebound stage in frontal impact 9/12
Minimising slip on the shoulder harness adjuster during front and side impacts (critical feature) 9/9
-$10 with Welcome = $110 :)