Keep in mind that AGP has been known to be very quirky/poorly implemented on many motherboards, so it may take fiddling to get it to work (i.e. specifying a particular AGP mode in the xorg.conf) devs are still chasing down these quirks so they can be detected and handled in the driver automatically, so if you have this problem, be sure to tell the devs.
No they don't anymore, Nvidia went ahead in their rebranding game. The 780a is something else entirely now (980a SLI). The demand for the old lowly 780a chipset was going down, but now see all the buyers rushing to get the new 980a SLI
Geez, it's 2 hundred numbers more, it must clearly be a better chip.