$2000? That's 4x as much as what my computer cost. You have a large budget for a performance desktop. Mine cost around $500 (estimated from £300) and it can run BF3 on max graphics and highest res settings.
My spec:
OS: Windows 7 Ultimate 64-bit (6.1, Build 7600)
Manufacturer: Gigabyte Technology Co., Ltd.
System Model: H61M-S2-B3
BIOS: Award Modular BIOS v6.00PG
Processor: Intel(R) Core(TM) i3-2100 CPU @ 3.10GHz (4CPUs), ~3.1GHz
Memory: 4096GB RAM
DirectX Version: DirectX 11
Graphics info:
Name: AMD Radeon HD 6700 Series (6770 + fac. overclock)
Manufacturer: Advanced Micro Devices, Inc.
Chip Type: ATI display adapter (0x68BA)
DAC Type: Internal DAC(400MHz)
Total Memory: 2798 MB
Display Mode: 1340x1024 (32 bit) (60Hz)
Monitor: Generic Non-PnP Monitor
If I were you, I'd get something similar to this, but with an i7 and 6990 if you're looking for a mega monster.