Not great, but thats the same with every system really
At that res, i'd run at medium with no AA for a "playable" frame rate.
You'll just have to try and see tbh. You'll definatly be able to play it! My mate completed it with a 7600GT, and a 3800x2. As for DX10, you need not worry about that, because i'm pretty sure the 7 series dont support it!
1680x1050 res - Hows it going to do