Alright I think its safe to say we probably all have at least once messed around with an Xorg/Xf86 config file and were booted into a black screen with a basic oops you screwed up message.Over the past years I always saved my original to another directory along with any other versions that I got working. Like on my suse 10.2 box I have one for beryl and one for my tv-out then I issue a "cd /directory/xorg/" then "cp xorg.conf /etc/X11/" and all is good.Now there has got to be an even easier way to do this. Am I wrong?

If you know where the directory is just issue the command from where you are, e.g. cp /<file location>/xorg.conf /etc/X11 or you could create a shell script that when ran will copy the file to the location.

What I was actually looking for is setting up kdm/gdm to allow me to switch between 2 different xorg files. ex. Beryl and standard nvidia. My main reason is my desktop is linked to 2 sources my LCD which works perfect with beryl.And my tv which I use to play games or watch movies. If I have all the options beryl/compiz needs to run then even with beryl disabled my fps is lower than just my standard nvidia xorg.
My laptop I would like to add the option to switch between nvidia and nv driver.That card says it supported by nvidia but the computer only locks up with the nvidia driver the nv driver works perfect.
What I wrote above was for those occasions where my xorg.conf gets so messed up I cannot get to a login screen. Which doesn't happen often.But with all the different distros having there own methods of setting up your video display I resorted to my own method. I have 3 computers all with a different distro Fedora/Debian/Suse. And use to have Mandy also, I got tired of XFdrake and suse's Sax2 sorry that can be even more of a headache all depends on the hardware.

Just wrap them in a shell script. The shell script first copies the correct xorg.conf file into place then invokes the window manager.

When you see KDM/GDM, X is already started. So I doubt very much that it can be done from within the display manager; drivers, refresh rates, resolutions, it's already configured at that point so you have to restart X.
I'm not familiar with Beryl/Compiz (I don't know how they affect config files).

If you want to decide at boot time what option to use (so before X has started), you can analyse how your systems start X and modify a file in the bootup sequence to prompt the user.
Currently I only have Slackware10.1 at hand, where I can modify the file /etc/rc.d/rc.4. And there indeed copy or link xorg.conf