What you might want to do is work with creating .X objects. The reason being is that if you can wait for the next patch it will bring Octree support.
What this means is that you can take and load in your .x model and then add it to the octree(called Nodetree in DBPro), this will add in things like portals so can make high polygon worlds that are insanely large. You can do this without any conversion at all.
Here is a link to show you how Octrees work...
http://www.flipcode.com/tutorials/tut_octrees.shtml
Now on top of using octree's there is an advanced portal system as well, they are optimizing the code and getting any last minute bug out right now.
This also includes full on collision for DBPro's Nodetree's and you can add pixel shaders and such in as well as lightmaps with shadows.
Dark Basic Pro - The Bedroom Coder's Language of choice for the 21st Century.