The recommended (ie for best performance) would be a Raedon 5570 or better.
The minimum is a Gforce 8800. Your card is equal to a Gforce 9500 so it should work fine at minimal GFX settings. I do not know if the fact that it is an integrated chip as opposed to a stand alone card is an issue or not.
I wouldn't buy another card solely for this game. I'd only do it if you were going to upgrade anyhow. Ideally you want a GFX card with at least 1 gig of ram.
Take this advice how you want. Also, please note the following
* This is merely my personal opinion. I am NOT a developer nor do I work for Reverie Studios.
Advisers are NOT employees of or affiliated in any way with Reverie World Studios. We are merely fans just like you who attempt to help other players as best we are able to.