4K Nvidia Quadro K600 1GB PCIe x16 Graphics Card IBM 03T8309 [Quadro K600] - $89.00 : Professional Multi Monitor Workstations, Graphics Card Experts
Amazon.com: NVIDIA Quadro 4000 for Mac by PNY 2GB GDDR5 PCI Express Gen 2 x16 DVI-I DL, DisplayPort and Stereo OpenGL, DirectX (Boot Camp), CUDA and OpenCL Profesional Graphics Board, VCQ4000MAC-PB :
NVIDIA announces Quadro K5000 for Mac Pro, brings 4K support, 2x performance over Quadro 4000 | Engadget