AverageGuy got the gist of it. Consumer cards are geared for speed rather than image quality and precision.
For example, my Quadro has hardware line antialiasing, 8 window buffers for overlaid 3D perspectives, and dual DVI output. There are others with quad-DVI output, but you're reaching into serious priciness there. Even my Matrox G200 MMS still commands a ~$75 tag on FleaBay.
- M4H