[Build Help] Gaming PC in Australia

Hey guys, I'm looking into building a new rig for gaming (my curent one is a dell prebuilt from ~4 years ago)

I've gone through and researched some stuff and pulled out the parts list below so far, but I'm the first to admit I'm a noob when it comes to figuring out what's best in terms of hardware.

I'm missing a power supply and case at the moment as those are the parts I'm really unsure on, so suggestions on those would be very gladly accepted - as well as just general improvements or parts I could step down to save some money. Upper budget at the moment is around AU$1800, but the less the better.

Pretty much looking for a gaming rig that can run most current games on high/max - and using a dual monitor setup (maybe triple, if anyone can explain how that works?) Monitors/peripherals I'm buying separately on a separate budget (and using my current ones until then)

I am also located quite close to Umart (brisbane) but PCPartPicker doesn't have that as an option, I will be checking them first for lower prices before buying anything.

PCPartPicker part list / Price breakdown by merchant / Benchmarks

Type	Item	Price
CPU	Intel Core i5-3570K 3.4GHz Quad-Core Processor	$229.00 @ PCCaseGear
CPU Cooler	Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler	$36.00 @ Mwave Australia
Motherboard	Gigabyte GA-Z77X-UD5H ATX LGA1155 Motherboard	$249.00 @ PCCaseGear
Memory	Corsair Vengeance 16GB (2 x 8GB) DDR3-1600 Memory	$99.00 @ Mwave Australia
Storage	Corsair Force Series GT 120GB 2.5" Solid State Disk	$125.00 @ Mwave Australia
Storage	Seagate Barracuda 3TB 3.5" 7200RPM Internal Hard Drive	$149.00 @ PCCaseGear
Video Card	Gigabyte Radeon HD 7870 2GB Video Card (CrossFire)	$249.00 @ PCCaseGear
Video Card	Gigabyte Radeon HD 7870 2GB Video Card (CrossFire)	$249.00 @ PCCaseGear
Optical Drive	LG BH14NS40 Blu-Ray/DVD/CD Writer	$79.00 @ PCCaseGear
	Total
Prices include shipping, taxes, and discounts when available.	$1464.00
Generated by PCPartPicker 2013-01-02 18:47 EST+1100