Well, just so you know, in a couple of months, socket 939 will be obselete with the m2's. I personally would wait. But, if you absolutely cannot, then, yes, a 6800gs can fit in a socket 939. AS long as that mobo is agp.
i wouldnt say theyre going to become obsolete, im gona stick with 939 for a while longer because all those nice dual core cpus are gona get cheaper
ASUS P6X58D premium | i7 920 D0 @ 4.2GHz | Corsair XMS3 6GB | MSI GTX460 HAWK | OCZ vertex 2 SSD | Coolermaster HAF X case