Here is a list of all currently available graphics cards that are DirectX 11 capable, along with links to product details for each, courtesy of Amazon.
This list, revision 19, is current as of April, 2014. The list contains GPUs that span every possible price point from $60 entry level cards to the highest-end gaming card available at over $1000. While having DX11 this means they can display the latest effects, you aren’t going to find good 3D graphics or video encoding/decoding on, say, an HD 5450.
DX11 was available starting on on Windows 7 or Windows Vista SP 2
Workstation Card List
Want professional Workstation Cards? See the full list of DX11 workstation cards.