Well, I think with this build you'll be able to run just any game you want at just about any settings, so long as it's not a 4K monitor or three monitors with higher than 1080 resolutions. Of course, if you ever upgrade your displays it's a simple matter of adding an additional GPU and you'll pretty much be set for anything.
I don't think you'll need to upgrade anything, anytime soon with this build unless you decide at some point you need to drive higher resolution displays in which case an additional GPU for SLI would be fine. Might even be able to add one now if you really wanted and still be around your budget.
To the nitty gritty.
CPU has four cores and eight threads. Higher single core performance than any other CPU on Passmark. Since it has eight of them, you do the math.
https://www.cpubenchmark.net/singleThread.html
16GB of fast 2133mhz RAM. You can add another 16GB down the road if you should ever decide you need to but unless you're running virtual machines or some very high end applications simultaneously, I doubt you'll need to.
Very good ASUS motherboard without all the fancy colors and unnecessary markings of the gaming boards, but still has great features like 12 phase power which will allow for an optimal overclocking experience should you choose to do so, an M.2 slot if you should decide to add an M.2 SSD or M.2 Wi-Fi card. It also has pretty good onboard sound with audio shielding to reduce interference and electrical noise. You may not need a separate sound card unless you're into enthusiast or professional grade sound editing or recording.
http://www.asus.com/us/Motherboards/Z97PRO/overview/
Very decent Noctua cooler. You should have no problem taking that CPU to 4.5Ghz with this cooler and case cooling combination, if you choose to. If not, it's still about ten times better than the stock cooler.
Very reliable and fast Samsung 256GB SSD for the OS and applications. 2TB HDD for storage.
Gigabyte G1 gaming GTX 970 GPU. This speaks for itself.
Phanteks Enthoo Luxe full tower case. This is arguably the best case available under 150.00 by any manufacturer. There are better full towers and bigger ones too, but this will accommodate pretty much any cooling solution you want to install for the CPU and has plenty of fan locations and an optimized internal arrangement that facilitates cooling and has good cable management features.
I also added two additional case fans since the case only comes with three. These are for the two top locations that don't come with fans pre-installed. I'd recommend connecting the front 200mm preinstalled fan and all three top fans to the four PWM motherboard case fan headers on the board and the rear exhaust fan to the CPU OPT (Secondary cpu fan header on the motherboard) header as it only comes with four chassis fan headers. This will also allow the rear fan to run at a speed that is proportional to the cpu temp and thusly, the cpu fan. When the cpu fan is running slow there is less need for this fan to be running all out but when the cpu fan ramps up the rear exhaust fan will increase along with it.
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel Core i7-4790K 4.0GHz Quad-Core Processor ($318.99 @ SuperBiiz)
CPU Cooler: Noctua NH-U14S 55.0 CFM CPU Cooler ($69.98 @ OutletPC)
Motherboard: Asus Z97-PRO ATX LGA1150 Motherboard ($168.98 @ Newegg)
Memory: G.Skill Ripjaws X Series 16GB (2 x 8GB) DDR3-2133 Memory ($159.98 @ Newegg)
Storage: Samsung 850 Pro Series 256GB 2.5" Solid State Drive ($169.99 @ NCIX US)
Storage: Western Digital BLACK SERIES 2TB 3.5" 7200RPM Internal Hard Drive ($124.00 @ Amazon)
Video Card: Gigabyte GeForce GTX 970 4GB WINDFORCE Video Card ($359.99 @ Amazon)
Case: Phanteks Enthoo Luxe ATX Full Tower Case ($149.99 @ Amazon)
Power Supply: EVGA 750W 80+ Gold Certified Fully-Modular ATX Power Supply ($108.99 @ SuperBiiz)
Optical Drive: Asus DRW-24B3ST/BLK/G/AS DVD/CD Writer ($22.29 @ OutletPC)
Operating System: Microsoft Windows 8.1 - 64-bit (OEM) (64-bit) ($92.00 @ B&H)
Case Fan: Noctua NF-P14r redux-1500 PWM 78.7 CFM 140mm Fan ($18.89 @ Amazon)
Case Fan: Noctua NF-P14r redux-1500 PWM 78.7 CFM 140mm Fan ($18.89 @ Amazon)
Total: $1782.96
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-01-07 01:57 EST-0500
The actual cost of this unit may likely be a bit less when all is said and done, if you follow up on any mail in rebates, as I did not include those in the price.