yes the fact that it is an integrated gpu tells me its not good. i have a radeon 5870 which runs the game perfect, its a little pricy though. A radeon 5770 should run the game pretty good too and cost about $100.00 online, maybe cheaper if you look around. If you are looking at the minimum price best performance you may want to start another thread just for that so people can help you.
The good news is the rest of your pc seems up to date.

Also, have you run the bench mark test. Its not 100 percent accurate but i believe they also give you the minimum gpus required.