according to this dx9 is now 166 meg
I think they just chose that number specificly for it's suggestive evilness. Having DX9 as a requirement for your game isn't that big of a problem if your game comes on a CD or DVD and your game installation detects and trigger the DX9 installation if it's missing.
Ofcourse the requirement isn't DirectX9. The requirement is OpenGL *or* DirectX9. So you've got quite a lot of systems covered, old aswell as new.