Actually, the nVidia 6000 series support Pixel Shading 3.0, which is part of DirectX9 I think.
For the topic creator, yes Windows 7 will definitely work with games that uses Direct X7 and above.
Although there's a minor chance that certain games will not work due to changes between Windows XP to windows 7. But is not related to the DirectX version used.
To be sure, download the latest redistributable DirectX9 installation, this will update the files needed.