oh my oh my, things are a bit pricey there in kangaroolandia. alright
first of all, the graphics card is not available in that store you chose. second of all, i would recommend getting 2 sticks of 4GB instead of 1 stick of 8GB because if you have 2 or 4 sticks, ram runs in dual-channel mode, aka twice the speed
can't help you much more than that since i have no clue about the pricing of parts there
but if you can, you should probably get the r7 270x which i found for about 20 bucks more at your australian store
http://www.scorptec.com.au/computer/51912-his-r9270x-2gd5its about 20% to 30% better than the 650ti from what i've seen