My gaming rig - Opinions please?

@A12MO12
Couple comments. First and foremost, a 980Ti is waaaaayyyy too much horsepower for gaming in 1080. A 970 is best for that resolution. Second, the OP is based out of Australia, so prices are significantly higher than in the US.

@OP. I have a few suggestions for changes. As A12MO12 pointed out, your build lacks a GPU, which is generally the most expensive component of a gaming build.
Secondly, if your main task is gaming, you will see no performance gains between an i5 and an i7, so you can drop down to an i5 to put more money towards a GPU.

You picked out a very good PSU, but you won't need anywhere near 900 watts. A 620 is more than enough and will leave you room for overclocking.

The only reason why I didn't drop you down to 8GB of RAM is because I suspect that RAM prices will go up, especially down where you and 8GB will be a cap are in a couple years.

You don't want the red series from WD as it's more focused on NAS storage applications. The Black series are arguably the best hard drives on the market.

I recommended a Ducky keyboard because they're one of the best brands out there and if I could pick the best all around mechanical key, I would say browns are the best of both worlds for gaming and typing.

As far as the mouse goes, it's up to you, just get one with good reviews. I personally have a Logitech G700 and I love it.

This build comes in a little over your price, but you can hold off on the headphones until you have the funds. (I have a set, best audio equipment I've ever owned, highly recommend when you have the money)

If you have any questions, let me know. Cheers.

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor ($324.00 @ Centre Com)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($65.00 @ CPL Online)
Motherboard: Gigabyte GA-Z97X-Gaming 3 ATX LGA1150 Motherboard ($199.00 @ CPL Online)
Memory: G.Skill Ripjaws X Series 16GB (2 x 8GB) DDR3-1600 Memory ($144.00 @ IJK)
Storage: Samsung 850 EVO-Series 500GB 2.5" Solid State Drive ($268.00 @ IJK)
Storage: Western Digital BLACK SERIES 3TB 3.5" 7200RPM Internal Hard Drive ($219.00 @ Centre Com)
Video Card: Gigabyte Radeon R9 390 8GB SOC Video Card ($499.00 @ CPL Online)
Case: NZXT Phantom 410 (Black/Orange) ATX Mid Tower Case ($129.00 @ CPL Online)
Power Supply: Antec High Current Gamer 620W 80+ Bronze Certified Semi-Modular ATX Power Supply ($119.00 @ Umart)
Optical Drive: LG GH24NS90 DVD/CD Writer ($29.00 @ CPL Online)
Monitor: LG 25UM57-P 60Hz 25.0" Monitor ($279.00 @ Mwave Australia)
Keyboard: Ducky DK9008 Shine 3 White LED Backlit (Brown Cherry MX) Wired Standard Keyboard ($129.00 @ CPL Online)
Mouse: Razer DeathAdder 2013 Wired Optical Mouse ($49.00 @ CPL Online)
Headphones: Kingston HyperX Cloud Headset ($99.00 @ Umart)
Speakers: Logitech Z313 25W 2.1ch Speakers ($59.00 @ Centre Com)
Total: $2610.00
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-07-14 00:22 AEST+1000

EDIT: I mentioned that a 970 is best at 1080p, then recommended a 390. This is because I fear that the segmented memory of the 970 would be an issue at 2560x1080. Also, the 8GB of VRAM of the 390 is more than enough.

you have no graphics card? I will try to put together a build for $2500 with everything. Will edit it in once I finish it.

EDIT: one of the best graphics card which can be used for1440p or 4k. Included solid mouse + keyboard and the headset is one of the best if you consider the performance for the price. Monitor is 1080p with 144 Hz refresh rate. Does not include speakers or mouse mat (can get decent mouse mat for ~$20).

EDIT 2: did not know OP was in Australia, this component selection would be over $3000 there.

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i7-4790K 4.0GHz Quad-Core Processor ($318.99 @ SuperBiiz)
CPU Cooler: Noctua NH-D15 82.5 CFM CPU Cooler ($89.75 @ OutletPC)
Motherboard: Asus MAXIMUS VII HERO ATX LGA1150 Motherboard ($208.99 @ NCIX US)
Memory: G.Skill Ripjaws Z Series 16GB (4 x 4GB) DDR3-1866 Memory ($109.99 @ Newegg)
Storage: Samsung 850 EVO-Series 500GB 2.5" Solid State Drive ($161.99 @ Amazon)
Storage: Western Digital Caviar Black 2TB 3.5" 7200RPM Internal Hard Drive ($142.45 @ OutletPC)
Video Card: EVGA GeForce GTX 980 Ti 6GB Superclocked+ ACX 2.0+ Video Card ($679.99 @ NCIX US)
Case: NZXT H440 (Black/Red) ATX Mid Tower Case ($104.99 @ Micro Center)
Power Supply: SeaSonic G-750 750W 80+ Gold Certified Semi-Modular ATX Power Supply ($104.99 @ NCIX US)
Operating System: Microsoft Windows 7 Home Premium SP1 OEM (64-bit) ($89.91 @ NCIX US)
Wireless Network Adapter: TP-Link TL-WDN4800 802.11a/b/g/n PCI-Express x1 Wi-Fi Adapter ($37.24 @ Amazon)
Monitor: Asus VG248QE 144Hz 24.0" Monitor ($249.99 @ Amazon)
Keyboard: Logitech G710 Wired Gaming Keyboard ($94.99 @ NCIX US)
Mouse: Logitech G502 Wired Optical Mouse ($59.00 @ NCIX US)
Headphones: Kingston HyperX Cloud Pro Headset ($79.99 @ Amazon)
Total: $2533.25
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-07-13 09:57 EDT-0400