War, it looks like XF86Config is all screwed up for you. For starters, in the device section, if you don't have 'driver "nvidia"', then it won't even know to load the nvidia drivers.
In fact, I don't even know how the computer knows what drivers to load at all.
It may be that you're actually using a different configuration file all together.
Check out /var/log/XFree86.0.log, early in there, you should see a line like this:
(==) Using config file: "/etc/X11/XF86Config"
Except, you might be using a different config file. Whatever it says it's using, take a look at that file, and see if it makes more sense (i.e., you have place to load those modules, you have a driver that you can change to nvidia)
Also, look through the log file--there may be errors in there that can give you a clue as to what's up.