Get the i5 2500k if you are going for a gaming rig with a dedicated GPU card. Ivy bridge of the 3570k isn't worth the money in terms of performance gain.
Also for graphic cards, look up performance charts on review site before buying em as the actual size of the onboard RAM are not a good indicator of the performance you can get from them.
I just recently built myself a rig for around 1.2k USD (being a malaysian, price is slightly higher but not by a lot) and here's the spec i'm using.
PCPartPicker part list:
http://pcpartpicker.com/p/bigg
Price breakdown by merchant:
http://pcpartpicker.com/p/bigg/by_merchant/
Benchmarks:
http://pcpartpicker.com/p/bigg/benchmarks/
CPU: Intel Core i5-2500K 3.3GHz Quad-Core Processor ($169.99 @ Microcenter)
Motherboard: Asus P8Z77-V ATX LGA1155 Motherboard ($169.87 @ Newegg)
Memory: Corsair XMS3 8GB (2 x 4GB) DDR3-1333 Memory ($36.98 @ NCIX US)
Hard Drive: Western Digital Caviar Black 1TB 3.5" 7200RPM Internal Hard Drive ($102.99 @ SuperBiiz)
Video Card: MSI GeForce GTX 670 2GB Video Card ($369.99 @ Newegg)
Case: Cooler Master Elite 430 ATX Mid Tower Case ($34.99 @ Newegg)
Power Supply: Silverstone 600W ATX12V / EPS12V Power Supply ($59.98 @ NCIX US)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($16.99 @ Newegg)
Total: $961.78
(Prices include shipping and discounts when available.)
(Generated by PCPartPicker 2012-07-27 06:43 EDT-0400)
I used this
guide for reference when planning my rig.