I'd also like to throw in my own computer recommendation:
http://pcpartpicker.com/p/pKzZ
CPU i5-3570K $219.99
http://pcpartpicker.com/part/intel-cpu-bx80637i53570k
CPU Cooler TUNIQ Tower 120 Extreme $64.99
http://pcpartpicker.com/part/tuniq-cpu-cooler-crt120exbkrv1
Motherboard ASRock Z77 Extreme4 ATX $104.99
http://pcpartpicker.com/part/asrock-motherboard-z77extreme4
Memory G.Skill Ripjaws X Series 2x4GB F3-14900CL9D-8GBXL $29.99
http://pcpartpicker.com/part/gskill-memory-f314900cl9d8gbxl
Storage Seagate Barracuda ST2000DM001 2TB 7.2KRPM $69.99
http://pcpartpicker.com/part/seagate-internal-hard-drive-st2000dm001
Samsung 830 Series 256GB $169.95
http://pcpartpicker.com/part/samsung-internal-hard-drive-mz7pc256nam
Video Card X2 (CFX) Sapphire Radeon 7950 100352VXSR $329.99x2=$659.98
http://pcpartpicker.com/part/sapphire-video-card-100352vxsr
Case Antec Nine Hundred Two V3 ATX Mid $96.99
http://pcpartpicker.com/part/antec-case-ninehundredtwov3
Power Supply SeaSonic SS-750KM 750W 80 PLUS Gold $99.99
http://pcpartpicker.com/part/seasonic-power-supply-ss750km
Optical Drive Samsung SH-224BB DVD/CD Writer $15.99
http://pcpartpicker.com/part/samsung-optical-drive-sh224bb
Operating System Microsoft Windows 8 (OEM) (64-bit) $79.98
http://pcpartpicker.com/part/microsoft-os-wn700404
The i5-3570K doesn't need an introduction.
The Ivy K edition CPUs don't get very hot, so they need a very thermally conductive cooler, not a cooler that can manage a ton of heat without getting obtusely hot. So, Direct Touch Heatpipes are almost entirely a must for optimal thermals. This high-end cooler provides them as well as good noise and thermal load. Almost all other high-end coolers lack Direct touch Heatpipes, which although not a big issue for most other CPUs, can be an issue for Ivy Bridge CPUs in overclocking.
I see little reason to go beyond the ASRock Z77 Extreme 4. It's a fairly high end board despite its low end price and anyone who has had one and compared to several much more expensive Z77 boards can usually attest to that. A much more expensive board may be able to beat it, but don't expect a return that's worth the payout. Ivy is still much more limited by thermals than by the motherboard's power delivery and that it's already so high-end makes even the most extreme graphics systems usually not troubled by the i5-3570K with a moderate overclock. This system should have no trouble with afairly extreme overclock anyway.
This memory kit is the best and cheapest used in the builds that I've seen here so far. You could drop another $10 for an otherwise identical DDR3-1600 kit, but when it's a mere $10 with a $2000 budget, the small performance boost is worth the minuscule price premium.
Some others mentioned this hard drive earlier IIRC and really, it's pretty good. I prefer Western Digital, but Western Digital has no reasonably priced 2TB 7.2KRPM models and Seagate Barracuda is the next best in this example.
Samsung 830 continues to be among the best SSDs in almost every way except for write performance. I'd prefer Vertex 4 overall, but Vertex 4 is priced much higher right now.
These 7950s are cheaper than any non-reference, similarly performing to most 670s (even most non-reference models) at stock, and superior overclockers with comparable power efficiency at the same level of performance. It's a meet or win all around when the free games are considered.
I opted for a superior Seasonic 80+ Gold PSU than the others here that just happens to have an incredible price ATM.
The case is much more subjective. I can't justify spending more on the case than about $100 and this excellent Antec case fits nearly perfectly in that.
Paying more for an optical drive doesn't matter unless you want more features (Blu-Ray support, M-Disk support, etc), so I went for the cheapest DVD writer (technically, this is one cent more expensive than the cheapest, but a little better thna the cheapest and the penny is worth it).
I went for Windows 8 (OEM) x64 as the OS like some others did before me. I consider it to be a superior OS than 7 and it has been proven to be superior under the hood. If you dislike the UI, then install Classic Shell (which is free) and you can get back the start menu, boot directly into the desktop, re-install Aero, and much more with it.