Because I'm like a gay guy helping their bezzie girlfriend go clothes shopping when it comes to PC shopping, feast your eyes on this beast.
PCPartPicker part list /
Price breakdown by merchant /
Benchmarks
CPU: Intel Core i5-3570K 3.4GHz Quad-Core Processor ($169.99 @ Microcenter)
Motherboard: Asus Maximus V Gene Micro ATX LGA1155 Motherboard ($199.99 @ Microcenter)
Memory: Patriot Intel Extreme Master, Limited Ed 8GB (2 x 4GB) DDR3-1600 Memory ($32.99 @ Newegg)
Storage: Samsung Spinpoint F3 1TB 3.5" 7200RPM Internal Hard Drive ($88.98 @ Newegg)
Storage: Samsung 830 Series 64GB 2.5" Solid State Disk ($56.97 @ Newegg)
Video Card: EVGA GeForce GTX 660 Ti 2GB Video Card ($279.99 @ NCIX US)
Case: Cooler Master HAF 922 ATX Mid Tower Case ($99.99 @ Amazon)
Power Supply: SeaSonic 650W 80 PLUS Gold Certified ATX12V / EPS12V Power Supply ($131.29 @ Newegg)
Optical Drive: Asus BW-12B1ST/BLK/G/AS Blu-Ray/DVD/CD Writer ($62.50 @ NCIX US)
Total: $1122.69
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2012-11-15 12:43 EST-0500)
Obvious areas to skimp to save cash would be storage, either less mechanical storage or removing the SSD completely and the blu-ray writer.
This should run BF3 on Ultra fairly comfortably.
Haven't included a monitor/keyboard/mouse/speakers assuming you'd bring them from an old PC, but if you want a new gaming mouse and keyboard, my recommendations would be:
Best - Mouse: Roccat Kone[+] Keyboard: Razer Blackwidow Ultimate 2013 Elite (SUPER ULTRA HD REMIX... That fucking title)
Awesome Budget - Mouse: Logitech G500 Keyboard: Microsoft Sidewinder X4