Setting up a linux PC with an Intel 82815 controller as a home entertainment centre, using our Widescreen CRT JVC TC as the monitor turned out to be some deepdigging in the xorg.conf file. Well, what saved me was the gtf-application that can make modelines for xorg.conf, and the description on how to add them into xorg.conf.
gtf 640 480 60
gave a resonable mode line for the TV. When that was put into the monitor section and referenced in the screen section, I was quickly up and playing.