Need advice for my 1st PC Build

[Majesticness]

This will be a gaming build and I really am nervous about messing it up or something. My build is here http://pcpartpicker.com/p/xbrqXL . The parts I am really unsure about are my Power Supply and my Operating System. I do need advice on the other parts though. Also, my budget is $1,200 but it's ok if it goes over by a bit. Thanks in advance guys!

 

[dottorrent]

You're better off getting Windows 8.1 dude. It's faster, uses less resources and it's cheaper.

 

[r3v3ng3]

PCPartPicker part list: http://pcpartpicker.com/p/F68xCJ
Price breakdown by merchant: http://pcpartpicker.com/p/F68xCJ/by_merchant/

CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor ($219.75 @ OutletPC)
Motherboard: ASRock Z97 EXTREME4 ATX LGA1150 Motherboard ($119.99 @ Micro Center)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-2133 Memory ($64.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($47.89 @ OutletPC)
Video Card: MSI GeForce GTX 970 4GB Twin Frozr V Video Card ($329.99 @ Newegg)
Power Supply: XFX XTR 550W 80+ Gold Certified Fully-Modular ATX Power Supply ($66.98 @ Newegg)
Optical Drive: Samsung SH-224DB/BEBE DVD/CD Writer ($14.98 @ Newegg)
Operating System: Microsoft Windows 7 Home Premium SP1 (OEM) (64-bit) ($88.98 @ OutletPC)
Monitor: Asus VH238H 23.0" Monitor ($147.58 @ Newegg)
Keyboard: Cobra Polygon Wired Gaming Keyboard ($20.03 @ Mwave)
Mouse: Cobra Horizon Wireless Optical Mouse ($15.90 @ Newegg)
Other: Sentey Stealth Gaming Case ($54.99)
Total: $1192.05
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-03-04 18:47 EST-0500

The only thing you could possibly look to change in this build is the OS. As dottorrent said windows 8.1 performs better, but the difference in gaming is either non existent to very minute. Hence I prefer windows 7 due to its UI.

Also if you're happy to go $100 over, throw in a Crucial MX100 256gb SSD.

 

[Majesticness]

You're better off getting Windows 8.1 dude. It's faster, uses less resources and it's cheaper.

Thank you for the advice! Wish I could pick more then one solution, because this also helped a lot as well.