I think if you add say, a cheap ATi PCI card w/TV-out, I'm not sure that DVD's will play back through it, I've heard that the primary card is used for that, but I can't verify this.
If you want to blow a pile of money, get a 64MB Radeon ViVo, that's fast and has TV-in and TV-out.
For less money you can use a stand-alone scan converter to connect your existing video card output (or any video card output, for that matter) to a TV. One that has a good reputation is the AverKey imicro, which costs about $90. There are others that are a little less expensive, and others that are a lot more expensive. If you get one of these, you will always have TV-out no matter what video card you are using.