THe real limitation you are looking at here is your T.V., not your video card. S-video, while great for streaming video such as a DVD movie, is proof to me that the T.V. you are using is not HDTV.
The amount of lines that most T.V.s can produce is pretty pathetic, and totally unsuitable for text display, particularly if you are planning on using small fonts. I do not recommend that you purchase any video card and try to do this, it will not be readable and your will be very dissapointed.
There are other solutions out there. I'm not sure what you have access to, but digital projectors are awesome, even ones that are a couple years old. The cheaper/older ones have native reolutions of 800x600, and more expensive ones will get into the XGA (1024x768) range. Your can size your screen as big as you want, making it a lot easier to read smaller fonts. And, these all will take a normal SVGA 15-pin connection. If your don't have access to one, they are out there for rent, and it may be the best solution for you.
If you do have HDTV, you have to use a digital video card, as this is the way the T.V. can display the greater resolution. Anything else is analog, and you won't get enough lines in there to display text.
If you think about it, if T.V.s could display this, everyone would have a 35" monitor!
