Whoever posted a 3870, no, that card is old now. Maybe a 4830 or even 9600gt.
Yeah, and the 9600 GSO is so new that it automatically becomes the better card by default, right? The 3870 and 9600 GSO trade blows, so all is well.
Read the rest of my post and you'll realize that I settled for a build with the 4830 in it, so there goes the argument between the 9600 GSO and 3870.
Edit: I'm not sure of the exact difference either, but I do know that the 4830 performs near equivalently with the 8800GT, which is the same as the 9800 GT, which is stronger than the 9600 GT by a healthy margin. Up to you, that free game might be the deal breaker here.