Hae I am living in New Zealand and have a budget of $1200 NZD to build a gaming computer. I want to get all my parts from http://www.pbtech.co.nz as it is the cheapest and has the closest physical store i know of.
Any feedback on this setup would be greatly appreciated. My main concerns are the power supply and the PCI-2 16x on the motherboard for the graphics card because i am unsure whether if it would bottleneck the system.
if i were you i would look into a 990fx chipset board as they are better for overclocking and usually have more options for multi GPU set ups as well as a better power phase design.
Here, there are two things to remember: ONE. A better chipset will serve you well in the future, as it is more likely to support new standards and sockets later on (though in this case the standard's going to be FM2+ so why bother with that). TWO. Get a 3rd party cooler, even if it's only a Scythe Ninja 3 or Thermalright Macho. AMD stock fans are loud as hell and the cooling blocks don't cool very well (as in, they're made to stop the CPU from going over 80C when at the highest fan speed...).
The CPU is a good choice, BUT. I would go with the 8-core if you can manage to get the budget. Why is that, you ask? Well, you could disable half of the cores (every core with an odd number) in that to have a very nifty quad core CPU with one FPU per core (normally, Bulldozer only gives you one FPU per two cores, and a FPU is as far as I know pretty important for game performance; the front end of the CPU will also have to cope with less instructions per second, thus maybe making it more efficient). Then there's the fact that most games are only 4-threaded, so... I frankly don't see the point of lowering your performance by using 8 cores or 6 cores instead of a better option.
Go with one 8GB RAM stick. You're going to want to upgrade, and you're going to want to do it quite soon. Having more space free for RAM is good in this case.
Seagate HDDs: they have a bad reputation (even if it is one I have not been able to confirm myself, even if a lot of my HDDs are Seagate, and the one that's failing is from WD). The HDD you receive is probably going to be fine, just keep it in mind: you might have to return it for warranty.
The R9 280X is much better value for the money, if you can get one for only a bit more - know that the price/performance ratio is about the same for both cards, with the 270X occasionally having a worse price/performance ratio.
Power Supply looks to be adequate for the configuration. I can't really comment on the choice of case, since I don't use a case.
If you're not going to be upgrading the computer much, I'd stick with the build you have now. NZ prices are expensive!
If you're going to be upgrading the computer within a year or something, get a better chipset and crossfire support on the motherboard(990FX chipset, I think). Get 1 stick of 8 GB ram for future upgradeability, and upgrade your PSU to around 700w for capability of handling around 2 270Xs