Re: Resolution with S-Video
Composite and S-video are made for resolutions of upto about 800x600. Above that resolution you need relatively high frequency pixelclocks which the cables can't handle that well (leads to a lot of signal loss).
When you connect a tv using s-video the resolution the card outputs (in case of the integrated tvout encoder of Nvidia gpus) is 720x480 (NTSC) or 720x576 (PAL) no matter which resolution you specify in your xorg.conf. The image is scaled to fit into this view.
If you really want high resolutions for tvout (HDTV) you should use either component or hdmi/dvi.