Geometry vs Graphics

Hi. I want to buy a new pc and I’m thinking about using 2 graphics cards (someone said something that I thought would be interesting to try). So here are the questions:

  1. can one graphics card be used to do the graphics/textures and one to do the geometry (both being ATI cards: Radeon X1900XTX and Radeon HD5750)?
  2. (if yes to the first one) which one needs more processing power, texture or geometry?
    Thank you in advance. Bye.