Sonic, you might want to try out my demo of Terrascape - downloadable from the Beta announcements forum or the forums on my web page.
The reason I suggest it is because Terrascape proves that the method to a really very large map is not by making your matrix bigger, but instead smaller.
If you have a small matrix, the update matrix command does not take very long to execute and can be done every few seconds - thus dynamically changeing the contents of your matrix by keeping the camera central to the matrix itself.
In essence, you move the matrix around the camera, rather than the camera around the matrix (although I still move my camera and simply reposition my matrix - it's easier to do AI that way).
So there you have it, the ultimate secret to massively huge matrixes
As for distance culling, personally I automatically solved that one with my matrix world - because in order to fill that massive matrix with objects (anyone can make a big map - the problem is filling it) you have to be pretty dynamic with your content too so I manually cull my objects in the code (and re-use them so 1 tree object can show several trees), therefor erradicating the need to use set camera range at all.
Pneumatic Dryll, Outrageous epic cleric of EQ/Xev
God made the world in 7 days, but we're still waiting for the patch.
