AFAIK, the Gigabyte X800 XL is the most powerful of the fan-less video cards. It is much better for gaming than the other cards mentioned, and it actually plays all current games very welll at high resolutions and with eye candy turned on. Also, compared to those other cards, the X800 XL has a much better chance of performing well with games released in 2006 and even 2007. It's currently just under $300 on newegg. Here's a description:
http://www.hardwarezone.com/articles/view.php?id=1571&cid=3&pg=4
But if gaming is not a big concern, you can save a lot of cash by getting one of the other cards mentioned.
> What makes a vid card good?
When people on this forum compare video cards, they typically compare their performance in games. All other things being equal, the higher the framerate (frames per second or "FPS") for a given game or benchmark, the better the card. There are plenty of reviews on the internet that compare the framerates of different cards on different games. If a card can perform well in games, it's a good bet it can handle whatever other applications you throw at it. Also, in general, look for higher specs for core clock speed, memory speed, memory bit interface, amount of memory, type of memory, pixel pipelines, and vertex pipelines. But IMHO, measured framerates are more reliable performance indicators than specs.