Thats a toughy... I think that I would sell the 939 rig, because you'll get more money out of it. I think that you could sell that 9500 for like $80 american, but I think that I would rather get a new AM2+ mobo (SB750 chipset) and OC the 9500... its clock speeds wont be all that impressive(2.5-2.7GHz ish is my guess), but it is faster clock for clock, besides the fact that it has 4 cores.Then you'll be able to upgrade to a deneb at some point, without having to do anything else, which is why I think its a better choice... but thats just me.
Good luck with whatever you do.
Good luck with whatever you do.