Yea you are right that there is very little that even requires DX 10.1 at the moment--I was assuming you want to keep this a little while.
Any graphic card in your price range could run this pretty easily.
The initial system requirements for Darkfall are as follows:
Operating System: Windows XP, Vista
Processor: 2.5GHz Pentium 4, or equivalent
RAM: 1GB for Windows XP, 2GB for Windows Vista
Graphics Card: 128MB PixelShader 2.0 support
Hard Drive Space: 12 GB Free Space Minimum