Yup, an Athlon 64 3200 would be fine, and I don't think you'd notice a difference at all. You can consider the Asus K8N-E deluxe too, this one got an Nvidia chipset. Many people prefer these. Just read some documentation/reviews to choose the one that suits your need.
And, since it's very important in gaming, what kinda video card do you plan to get?
