there is something called price to performance where items will be the best performance per dollar. $600-$1000 is the best to be when your building a pc because you get the most out of your dollar. your not cheeping out anywhere, but your your not losing money on pieces that have a minimal performance gain considering their price. below after the parts list will be the rational of each piece.
PCPartPicker part list:
http://pcpartpicker.com/p/FXgCK8
Price breakdown by merchant: http://pcpartpicker.com/p/FXgCK8/by_merchant/
CPU: AMD FX-6300 3.5GHz 6-Core Processor ($96.99 @ Amazon)
Motherboard: ASRock 970 Extreme3 R2.0 ATX AM3+ Motherboard ($79.99 @ Micro Center)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1866 Memory ($74.98 @ OutletPC)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($54.98 @ Directron)
Video Card: Gigabyte Radeon R9 270X 2GB WINDFORCE Video Card ($173.99 @ NCIX US)
Case: NZXT S340 (Black) ATX Mid Tower Case ($64.99 @ Micro Center)
Power Supply: EVGA 600B 600W 80+ Bronze Certified ATX Power Supply ($44.99 @ NCIX US)
Total: $590.91
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-01-18 19:47 EST-0500
The Rationale:
the cpu: this is the best bang for the buck cpu and it will show its strength in gaming can't get much better at this price point.
Motherboard: since i have 4 systems with Asrock motherboards and never has one failed me in the past few years, i support them and they are a great brand.
Memory: 8 gbs is great and all you will need for gaming. g skill and crucial are the highest quality ram creators
storage: for storage, this is mainly reliability. i have never had a western digital drive fail within 5 years.
GPU: gigabyte is a reliable brand and the 270x is the best bang for the buck 1080p gaming card
case: best case for the budget, that is all
PSU: evga akes good power supplies but what makes me buy theirs is the wonderful customer service.
in terms of games and settings expect to be able to play everything at least at medium. lighter games will be played at ultra while games like crysis 3 can be played at medium. (NOTE: when i say play, i mean 60 fps+. i you can play at 30 FPS, then bump up the settings.)