If you can find one, the Asrock Dual Sata2 is one heck of a 939 mobo, i am runnign one with my x2 4800+
very oc and volt mod friendly, and its got a pcie 16 and an agp port, and uses the uli 1695 chipset which kicked nforce3's butt (which is why nvidia bought them out)
If that isnt to your tastes, i have a gigabyte k8nsc-939, it has nforce3 and and agp port
I could be easily convinced to box up the gigabyte, i got it from monarch a while back before i was able to get my hands on the asrock. The gigabyte is "new in box", opened for inspection, and had my CPU mounted in it, has never been fired up. Oh and since i run a peltiered rig, there is some dielectric grease in the socket but that wont bother anything for you, just makes the cpu look kinda sticky if you take it out, and teh stock retention frame has been removed, but since you are building it for gaming, why would you want the stock HSF?