Your best bet if you're buying new is something like this:
ATI Radeon X1650 Pro 512MB AGP - Aria Technology
or
PowerColor X1650 Pro 512MB DDR2 VGA DVI TV Out AGP Graphics Card - Ebuyer
Or look out for an nVidia 7600GS which is about the same (or 7600GT which is better still).
These will be plenty to run that game well, and a few more demanding games as well if needed (they are both a fair bit better than the 9800pro which is now a very old card).
AGP cards aren't being made anymore, so you're paying a little over the odds for them really - it can be well worth looking second hand for a bargain - such as in the classifieds section over by here-------->
Computer Classified Adverts - AVForums.com
Don't be tempted to actually buy a 9800pro though. If it's the minimum requirement, it won't run it too smoothly - whereas the above cards would

.