You'll need two DVB-S cards (I tried Twinhan), both with CI support, a CAM module and a satellite card.
I'm from the Netherlands as well, and I tried the thing you wish to accomplish. However I was unable to get the satellite card communication stable enough, after switching between a few channels, the card would freeze up, and no longer tune to the Dutch channels.
But hey, that was a few weeks ago, I noticed BDA driver updates and new updates to MediaPortal. If you are able to get it working, please let me know, I'm getting tired of the IR connection to the Topboxes