Are you talking about 2 Dual Core CPU's running on a Motherboard with 2 Sockets? with AGP & PCI Express?
Or are you just talking about (1) Dual Core CPU on a Motherboard with 1 Socket? with AGP & PCI Express?
The first one you absolutely WILL NOT find. Nor would there be a need for it in a NON-SERVER PC. If it was a server PC then I don't suppose you'd be interested in keeping a X800XT, which is a gaming GPU.
The second one is available. There are several Motherboards that have both AGP & PCI Express slots. They only have one CPU Socket. I've seen them for both LGA775 & Socket 939. There are a few for s478 also. As far as (1) Dual Core goes, you'd have to check with the mobo maker and find out if dualies are compatible. There might possibly be a BIOS flash.
But (2) Dual Core with (2) Sockets & AGP & PCI-Express? Never going to find that.