Okay, the A64s come in two flavours. One is the old socket 754. It had single channel ram. Now Amd has added 185 pins, to allow an extra memory channel (184 pins + 1 for power) That's s939. But they gave a lot of weight to dual channel memory, and it's just not that good.
As a result, the s754 3000+ is a better performer than the s939 3200+.
If you are going with AGP graphics, and not OCing, there is no advantage to S939. You may as well get the better performance, and more tried and true mobos of s754.
Pick up an Asus K8N, and a s754 3000. You will be glad you did.