Here's some really good advice from the Graphic section. I'd take it, this Don Woligrowski guy really knows his stuff. : )
"Best PCIe Card For ~$400: Tie
Two Radeon HD 4890 cards in CrossFire Configuration (Check Prices)
Good 1920x1200 performance, 2560x1600 in most titles with some lowered detail
2 x Radeon HD 4890 in CrossFire Configuration
Codename: 2 x RV770
Process: 55 nm
Universal Shaders: 1,600 (2 x 800)
Texture Units: 80 (2 x 40)
ROPs: 32 (2 x 16)
Memory Bus: 256-bit
Core Speed MHz: 850
Memory Speed MHz: 975 (3,900 effective)
DirectX/Shader Model: DX 10.1/SM 4.1
Two Radeon HD 4890 cards should, on average, perform on par or better than a single GeForce GTX 295, and the Radeons cost less. If you have a CrossFire motherboard and want some serious high-resolution performance, this is the way to go."