That board is socket 939 and they never produced quad's for it. The best cpu's they made for that were Athlon X2 4800+, FX60 and opteron 185 which all were dual core.
I don't think socket 939 has a quad core, but what would be your goal? If you could save some money and put together a budget build you would get far more out of it then spending money on a much older system.