I did buy that same Seagate Barracuda about 4 months ago. It worked but It had 1000's and 1000's of errors fresh out the box. Decided to RMA considering the terrible reviews and seagate shortening their warranty.
I would not spend $500 on a 1920 x 1080 Monitor. Its up to you though.
Id also buy an internal card reader for SD cards if you need it.
This will future proof in the respect that you now have a bigger case that can support water-cooling more readily (believe me, its worth going custom rather than a closed loop, both cost about the same as well down here) and can fit E-ATX boards if you wish to in the future. And good cases will last multiple builds, so its worth buying a good one.
Bigger PSU of superior quality to accommodate dual cards later (which the Extreme4 can support).
And some lights, because the rig glowing is essential.
Probably have a bit left over for extra fans and other Misc items.
Though you do lose out on the 120hz monitor. And if my current monitor means anything, a good one can last a good couple of years, and that Benq is definitely a good one.
To save a bit of cash, I advise buying your parts locally. PC Case Gear is based in Melbourne, so there will be a postage fee to get your components from there. If nothing else see if you can buy the case locally, as that is likely going to be the biggest shipping expense.
I dont know of any Sydney based stores, but using this search engine youl will find all of the ones with an online presence. Type in the component your looking for and select NSW, and it will find the cheapest price in the state. http://www.staticice.com.au/advanced.html