[glc]

With that budget, an i7 and dual video cards is a stretch and not necessary.

Right around $1000 with no peripherals or OS:

COOLER MASTER HAF 912 RC-912-KKN1 Black SECC/ ABS Plastic ATX Mid Tower Computer Case - Newegg.com

SeaSonic S12II 620 Bronze 620W ATX12V V2.3 / EPS 12V V2.91 80 PLUS BRONZE Certified Active PFC Power Supply - Newegg.com

ASUS P8Z77-V LK ATX Intel Motherboard with UEFI BIOS - Newegg.com

Intel Core i5-3350P Ivy Bridge 3.1GHz (3.3GHz Turbo) LGA 1155 69W Quad-Core Desktop Processor BX80637i53350P - Newegg.com

CORSAIR Vengeance 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Low Profile Desktop Memory Model CML8GX3M2A1600C9 - Newegg.com

Intel 520 Series SSDSC2CW120A3K5 - Newegg.com

Western Digital WD Black WD1002FAEX Internal Hard Drive - Newegg.com

LG Model GH24NS95 24X DVD Burner - Bare Drive Black - Newegg.com

Newegg.com - SAPPHIRE 100354OC-2L Radeon HD 7870 GHz Edition 2GB 256-bit GDDR5 PCI Express 3.0 x16 CrossFireX Support Video Card *OR*
ASUS GTX660 TI-DC2O-2GD5 GeForce GTX 660 Ti 2GB 192-bit GDDR5 PCI Express 3.0 x16 HDCP Ready SLI Support Video Card - Newegg.com