He can't get a 7970 for $500 NZD.... the 7950 is the best thing for around $500 NZD.
And no. there is not any better Nvidia cards for around the same price that gives better performance. The closest thing to the 7950 is a GTX 670 which costs around $80 NZD more on the website you linked.
Out of the ones that you showed, you should get the Gigabyte model since it's the highest factory clocked (and cheapest too) with a good cooler.