Unless you have a really good reason, don't use an analogue tuner card for mythtv- many analogue TV tuners put an extra load onto the CPU to sample and encode the video, amd the quality is not as good as digital, you don't get digital sound (Dolby 2 channel with surround, the digital version of the original Dolby Prologic is transmitted in Australia).
In Australia, you can go to http://www.dtvforum.info/index.php?s=7281ed4ab8277f1668dca411079b53b7&showforum=9
for some information.
I am in Perth and use 3x Kworld Vstream DVB-T PCI tuners with Mythtv (currently on special as "HD" at Jaycar though the chipset in it can only go up to SD!). Though they work you now have better options- I'd suggest the Technisat Airstar 2 as an HD tuner, from digitalnow (you can see posts by renura who owns this company) http://www.digitalnow.com.au/
. This is Linux supported, should be "out of the box" for recent Linuxes.
Also see this page for some more info http://www.digitalnow.com.au/dvb_setup.html