Never used Gainward, but have used a couple of Palit cards in the past with no trouble. I know Tom's used to use Gainward in some of their builds, but not recently that I have seen.
Are there other brands available? Like Zotac, MSI, EVGA, XFX,.. EVGA and MSI are generally the best and the other 3 are acceptable.
I think some of us Texas geeks need to come down there and smack around the Aussie computer suppliers. Yours is the 4th or 5th recent post where selection was limited. I mean it's not like you guys are that far from Taiwan where much of this stuff ships from. Jeesh!
Gigabyte is not much better that the two you mentioned. Likely it is the dual fan model which costs extra. It is OK, but sort of a cheap copy of the MSI Twin Frozr cards that are all the rage.
I have been running a Gainward GTX 570 for some time now, and have been happy with my purchase, it runs cool and relatively quiet under load.
Palit is the parent company of Gainward.
I knew there was something about that name. I do not think they sell Gainward in the US as I do not recall ever seeing one. I know they are popular in the UK.