Welcome about.
DirectX is an Microsoft API, and isn't tied to Nvidia. It's manufacturer agnostic. DirectX 11 has been around since 2009, so I'd suspect it's just natural progression.
Pretty much all newer hardware is DX11 capable.
Edit;
That old Quadro FX 4800 in the title is only DX10 capable, and is EOL. It's a 2008 product. So you may want to consider an upgrade, beyond which the Quadro line is not intended for gaming. It's a workstation product.