Crusader...
With anything better than a Radeon 9000, and with 128Mb or more of onboard memory, this game will run very well. I recognize what everyone's saying about the 9600 and better cards, but you want to remember the crowd you're talking to here... serious gamers, who tend to want the best.
Again, I have a Radeon 9000 Pro 128Mb card with only 512Mb of ram, and this thing runs very well at about 80% of max settings. I mean really, it looks great and is very smooth, even without antialiasing on. Of course, it would be even better with a 9600 or higher.
While everyone would like to suggest that you go out and get a 9800 or higher, those are really not necessary. What often gets left out of this discussion is that if you get too powerful of a card, then you may very well need to add a new power supply to handle it, along with another intake or outake chassis fan to deal with the new heat. Just about every time I've made a major graphics card update to a newer technology level, it required getting a better power supply to handle it. That happened when I moved from the Radeon 7200 to the 9000.
Check out this site...
Power Supply Wattage Calculator
Fill out the test, then add a little headroom to the results for future upgrades.