Dell Small Business offers the AMD FirePro W7100 8GB GDDR5 Graphics Card, model no. W8XD5, bundled with a $300 Dell Gift Card for $829.99. Coupon code "SAVE35" cuts it to $604.49. (The gift card will display in your cart and be emailed 10 to 20 days from ship date.) Assuming you use the gift card and with free shipping, that's the lowest total price we could find by $526. It features up to 3.3 TFLOPS of computing power, up to 160GB/s memory bandwidth, 4K max display resolution, four DisplayPort outputs, and support for DirectX 12, OpenGL 4.4, OpenCL 2.0, and DirectGM.

Update: The price has increased to $902.09 before coupon, but it drops to $586.36 after.