You won't get the full experience. You're on the right track with AMD Radeon, but I would look for something in the 6000s range with at least 1GB of RAM. They'll be in the higher price range, but I'm running on an AMD Radeon 6450 and the game works great. I don't have it on full settings, however, because the factory card, the aforementioned card, only has 256MB RAM. If I had a greater amount of RAM, I'd be able to do full settings.
ALSO, and this is IMPORTANT, make sure your power supply (PCU) is at least 400W, anything less and the card will not run to peak performance. You can check that by opening up your computer and looking at the part where your computer plug goes. It should be on the side of that part, giving all the electrical information. That, or you could look the specs up online.
The above paragraph is just in case you don't know too much about computers. Not insulting anyone's intelligence here.