gday im also new to this. Heres some sites ive found with carputer related stuff here in oz
www.elx.com.au - have a number of pre-built barebones and full mini-itx systems and some other cool suff
auspcmarket.com.au - have a few different via mobos and some morex car psus. They also have a good collection of mini-itx cases.
as piabu said eyo.com.au has a fair few via boards (slightly cheaper then anywhere ealse ive found)
hope that helps